
This article demonstrates how to use the XML Type Provider to access XML documents
in a statically typed way. We first look at how the structure is inferred and then
demonstrate the provider by parsing a RSS feed.
The XML Type Provider provides statically typed access to XML documents.
It takes a sample document as an input (or document containing a root XML node with
multiple child nodes that are used as samples). The generated type can then be used
to read files with the same structure. If the loaded file does not match the structure
of the sample, a runtime error may occur (but only when accessing e.g. non-existing element).
Starting from version 3.0.0 there is also the option of using a schema (XSD) instead of
relying on samples.
The type provider is located in the FSharp.Data.dll
assembly. Assuming the assembly
is located in the ../../bin
directory, we can load it in F# Interactive as follows:
(note we also need a reference to System.Xml.Linq
, because the provider uses the
XDocument
type internally):
#r "System.Xml.Linq.dll"
open FSharp.Data
The XmlProvider<...>
takes one static parameter of type string
. The parameter can
be either a sample XML string or a sample file (relative to the current folder or online
accessible via http
or https
). It is not likely that this could lead to ambiguities.
The following sample generates a type that can read simple XML documents with a root node
containing two attributes:
type Author = XmlProvider<"""<author name="Paul Feyerabend" born="1924" />""">
let sample = Author.Parse("""<author name="Karl Popper" born="1902" />""")
printfn "%s (%d)" sample.Name sample.Born
The type provider generates a type Author
that has properties corresponding to the
attributes of the root element of the XML document. The types of the properties are
inferred based on the values in the sample document. In this case, the Name
property
has a type string
and Born
is int
.
XML is a quite flexible format, so we could represent the same document differently.
Instead of using attributes, we could use nested nodes (<name>
and <born>
nested
under <author>
) that directly contain the values:
type AuthorAlt = XmlProvider<"<author><name>Karl Popper</name><born>1902</born></author>">
let doc = "<author><name>Paul Feyerabend</name><born>1924</born></author>"
let sampleAlt = AuthorAlt.Parse(doc)
printfn "%s (%d)" sampleAlt.Name sampleAlt.Born
Paul Feyerabend (1924)
type AuthorAlt = XmlProvider<...>
val doc: string =
"<author><name>Paul Feyerabend</name><born>1924</born></author>"
val sampleAlt: XmlProvider<...>.Author =
<author>
<name>Paul Feyerabend</name>
<born>1924</born>
</author>
val it: unit = ()
|
The generated type provides exactly the same API for reading documents following this
convention (Note that you cannot use AuthorAlt
to parse samples that use the
first style - the implementation of the types differs, they just provide the same public API.)
The provider turns a node into a simply typed property only when the node contains just
a primitive value and has no children or attributes.
Now let's look at a number of examples that have more interesting structure. First of
all, what if a node contains some value, but also has some attributes?
type Detailed = XmlProvider<"""<author><name full="true">Karl Popper</name></author>""">
let info = Detailed.Parse("""<author><name full="false">Thomas Kuhn</name></author>""")
printfn "%s (full=%b)" info.Name.Value info.Name.Full
Thomas Kuhn (full=false)
type Detailed = XmlProvider<...>
val info: XmlProvider<...>.Author =
<author>
<name full="false">Thomas Kuhn</name>
</author>
val it: unit = ()
|
If the node cannot be represented as a simple type (like string
) then the provider
builds a new type with multiple properties. Here, it generates a property Full
(based on the name of the attribute) and infers its type to be boolean. Then it
adds a property with a (special) name Value
that returns the content of the element.
Another interesting case is when there are multiple nodes that contain just a
primitive value. The following example shows what happens when the root node
contains multiple <value>
nodes (note that if we leave out the parameter to the
Parse
method, the same text used for the schema will be used as the runtime value).
type Test = XmlProvider<"<root><value>1</value><value>3</value></root>">
for v in Test.GetSample().Values do
printfn "%d" v
The type provider generates a property Values
that returns an array with the
values - as the <value>
nodes do not contain any attributes or children, they
are turned into int
values and so the Values
property returns just int[]
!
In this section we look at an example that demonstrates how the type provider works
on a simple document that lists authors that write about a specific topic. The
sample document data/Writers.xml
looks as follows:
<authors topic="Philosophy of Science">
<author name="Paul Feyerabend" born="1924" />
<author name="Thomas Kuhn" />
</authors>
|
At runtime, we use the generated type provider to parse the following string
(which has the same structure as the sample document with the exception that
one of the author
nodes also contains a died
attribute):
let authors = """
<authors topic="Philosophy of Mathematics">
<author name="Bertrand Russell" />
<author name="Ludwig Wittgenstein" born="1889" />
<author name="Alfred North Whitehead" died="1947" />
</authors> """
When initializing the XmlProvider
, we can pass it a file name or a web URL.
The Load
and AsyncLoad
methods allows reading the data from a file or from a web resource. The
Parse
method takes the data as a string, so we can now print the information as follows:
[<Literal>]
let ResolutionFolder = __SOURCE_DIRECTORY__
type Authors = XmlProvider<"../data/Writers.xml", ResolutionFolder=ResolutionFolder>
let topic = Authors.Parse(authors)
printfn "%s" topic.Topic
for author in topic.Authors do
printf " - %s" author.Name
author.Born |> Option.iter (printf " (%d)")
printfn ""
Philosophy of Mathematics
- Bertrand Russell
- Ludwig Wittgenstein (1889)
- Alfred North Whitehead
[<Literal>]
val ResolutionFolder: string = "D:\a\FSharp.Data\FSharp.Data\docs\library"
type Authors = XmlProvider<...>
val topic: XmlProvider<...>.Authors =
<authors topic="Philosophy of Mathematics">
<author name="Bertrand Russell" />
<author name="Ludwig Wittgenstein" born="1889" />
<author name="Alfred North Whitehead" died="1947" />
</authors>
val it: unit = ()
|
The value topic
has a property Topic
(of type string
) which returns the value
of the attribute with the same name. It also has a property Authors
that returns
an array with all the authors. The Born
property is missing for some authors,
so it becomes option<int>
and we need to print it using Option.iter
.
The died
attribute was not present in the sample used for the inference, so we
cannot obtain it in a statically typed way (although it can still be obtained
dynamically using author.XElement.Attribute(XName.Get("died"))
).
In the examples shown earlier, an element was never (recursively) contained in an
element of the same name (for example <author>
never contained another <author>
).
However, when we work with documents such as XHTML files, this can often be the case.
Consider for example, the following sample (a simplified version of
data/HtmlBody.xml
):
<div id="root">
<span>Main text</span>
<div id="first">
<div>Second text</div>
</div>
</div>
|
Here, a <div>
element can contain other <div>
elements and it is quite clear that
they should all have the same type - we want to be able to write a recursive function
that processes <div>
elements. To make this possible, you need to set an optional
parameter Global
to true
:
type Html = XmlProvider<"../data/HtmlBody.xml", Global=true, ResolutionFolder=ResolutionFolder>
let html = Html.GetSample()
When the Global
parameter is true
, the type provider unifies all elements of the
same name. This means that all <div>
elements have the same type (with a union
of all attributes and all possible children nodes that appear in the sample document).
The type is located under a type Html
, so we can write a printDiv
function
that takes Html.Div
and acts as follows:
/// Prints the content of a <div> element
let rec printDiv (div:Html.Div) =
div.Spans |> Seq.iter (printfn "%s")
div.Divs |> Seq.iter printDiv
if div.Spans.Length = 0 && div.Divs.Length = 0 then
div.Value |> Option.iter (printfn "%s")
// Print the root <div> element with all children
printDiv html
Main text
First text
Another text
Second text
val printDiv: div: XmlProvider<...>.Div -> unit
val it: unit = ()
|
The function first prints all text included as <span>
(the element never has any
attributes in our sample, so it is inferred as string
), then it recursively prints
the content of all <div>
elements. If the element does not contain nested elements,
then we print the Value
(inner text).
In many cases we might want to define schema using a local sample file, but then directly
load the data from disk or from a URL either synchronously (with Load
) or asynchronously
(with AsyncLoad
).
For this example I am using the US Census data set from https://api.census.gov/data.xml
, a sample of
which I have used here for ../data/Census.xml
. This sample is greatly reduced from the live data, so
that it contains only the elements and attributes relevant to us:
<census-api
xmlns="http://thedataweb.rm.census.gov/api/discovery/"
xmlns:dcat="http://www.w3.org/ns/dcat#"
xmlns:dct="http://purl.org/dc/terms/">
<dct:dataset>
<dct:title>2006-2010 American Community Survey 5-Year Estimates</dct:title>
<dcat:distribution
dcat:accessURL="https://api.census.gov/data/2010/acs5">
</dcat:distribution>
</dct:dataset>
<dct:dataset>
<dct:title>2006-2010 American Community Survey 5-Year Estimates</dct:title>
<dcat:distribution
dcat:accessURL="https://api.census.gov/data/2010/acs5">
</dcat:distribution>
</dct:dataset>
</census-api>
|
When doing this for your scenario, be careful to ensure that enough data is given for the provider
to infer the schema correctly. For example, the first level <dct:dataset>
element must be included at
least twice for the provider to infer the Datasets
array rather than a single Dataset
object.
type Census = XmlProvider<"../data/Census.xml", ResolutionFolder=ResolutionFolder>
let data = Census.Load("https://api.census.gov/data.xml")
let apiLinks =
data.Datasets
|> Array.map (fun ds -> ds.Title,ds.Distribution.AccessUrl)
|> Array.truncate 10
type Census = XmlProvider<...>
val data: XmlProvider<...>.CensusApi =
<census-api xmlns="http://thedataweb.rm.census.gov/api/discovery/" xmlns:dcat="http://www.w3.org/ns/dcat#" xmlns:dct="http://purl.org/dc/terms/" xmlns:pod="https://project-open-data.cio.gov/v1.1/schema/" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:org="http://www.w3.org/ns/org#" xmlns:vcard="http://www.w3.org/2006/vcard/ns#">
<dct:dataset vintage="1999" geographyLink="http://api.census.gov/data/1999/nonemp/geography.xml" variablesLink="http://api.census.gov/data/1999/nonemp/variables.xml" tagsLink...
val apiLinks: (string * string)[] =
[|("1999 Nonemployer Statistics: Non Employer Statistics",
"http://api.census.gov/data/1999/nonemp");
("1997 Nonemployer Statistics: Non Employer Statistics",
"http://api.census.gov/data/1997/nonemp");
("1986 County Business Patterns: Business Patterns",
"http://api.census.gov/data/1986/cbp");
("1997 County Business Patterns - Zip Code Business Patterns: T"+[17 chars],
"http://api.census.gov/data/1997/zbp");
("1987 County Business Patterns: Business Patterns",
"http://api.census.gov/data/1987/cbp");
("1999 County Business Patterns - Zip Code Business Patterns: T"+[17 chars],
"http://api.census.gov/data/1999/zbp");
("1988 County Business Patterns: Business Patterns",
"http://api.census.gov/data/1988/cbp");
("2000 County Business Patterns: Business Patterns",
"http://api.census.gov/data/2000/cbp");
("1989 County Business Patterns: Business Patterns",
"http://api.census.gov/data/1989/cbp");
("1990 County Business Patterns: Business Patterns",
"http://api.census.gov/data/1990/cbp")|]
|
This US Census data is an interesting dataset with this top level API returning hundreds of other
datasets each with their own API. Here we use the Census data to get a list of titles and URLs for
the lower level APIs.
Let's go one step further and assume here a sligthly contrived but certainly plausible example where
we cache the Census URLs and refresh once in a while. Perhaps we want to load this in the background
and then post each link over (for example) a message queue.
This is where AsyncLoad
comes into play:
let enqueue (title,apiUrl) =
// do the real message enqueueing here instead of
printfn "%s -> %s" title apiUrl
// helper task which gets scheduled on some background thread somewhere...
let cacheJanitor() = async {
let! reloadData = Census.AsyncLoad("https://api.census.gov/data.xml")
reloadData.Datasets |> Array.map (fun ds -> ds.Title,ds.Distribution.AccessUrl)
|> Array.iter enqueue
}
val enqueue: title: string * apiUrl: string -> unit
val cacheJanitor: unit -> Async<unit>
|
To conclude this introduction with a more interesting example, let's look how to parse a
RSS feed. As discussed earlier, we can use relative paths or web addresses when calling
the type provider:
type Rss = XmlProvider<"http://tomasp.net/rss.xml">
This code builds a type Rss
that represents RSS feeds (with the features that are used
on http://tomasp.net
). The type Rss
provides static methods Parse
, Load
and AsyncLoad
to construct it - here, we just want to reuse the same URI of the schema, so we
use the GetSample
static method:
let blog = Rss.GetSample()
Printing the title of the RSS feed together with a list of recent posts is now quite
easy - you can simply type blog
followed by .
and see what the autocompletion
offers. The code looks like this:
// Title is a property returning string
printfn "%s" blog.Channel.Title
// Get all item nodes and print title with link
for item in blog.Channel.Items do
printfn " - %s (%s)" item.Title item.Link
Tomas Petricek - Languages and tools, open-source, philosophy of science and F# coding
- No-code, no thought? Substrates for simple programming for all (http://tomasp.net/blog/2022/no-code-substrates/)
- Pop-up from Hell: On the growing opacity of web programs (http://tomasp.net/blog/2021/popup-from-hell/)
- Software designers, not engineers: An interview from alternative universe (http://tomasp.net/blog/2021/software-designers/)
- Is deep learning a new kind of programming? Operationalistic look at programming (http://tomasp.net/blog/2020/learning-and-programming/)
- Creating interactive You Draw bar chart with Compost (http://tomasp.net/blog/2020/youdraw-compost-visualization/)
- Data exploration calculus: Capturing the essence of exploratory data scripting (http://tomasp.net/blog/2020/data-exploration-calculus/)
- On architecture, urban planning and software construction (http://tomasp.net/blog/2020/cities-and-programming/)
- What to teach as the first programming language and why (http://tomasp.net/blog/2019/first-language/)
- What should a Software Engineering course look like? (http://tomasp.net/blog/2019/software-engineering/)
- Write your own Excel in 100 lines of F# (http://tomasp.net/blog/2018/write-your-own-excel/)
- Programming as interaction: A new perspective for programming language research (http://tomasp.net/blog/2018/programming-interaction/)
- Would aliens understand lambda calculus? (http://tomasp.net/blog/2018/alien-lambda-calculus/)
- The design side of programming language design (http://tomasp.net/blog/2017/design-side-of-pl/)
- Getting started with The Gamma just got easier (http://tomasp.net/blog/2017/thegamma-getting-started/)
- Papers we Scrutinize: How to critically read papers (http://tomasp.net/blog/2017/papers-we-scrutinize/)
- The mythology of programming language ideas (http://tomasp.net/blog/2017/programming-mythology/)
- Towards open and transparent data-driven storytelling: Notes from my Alan Turing Institute talk (http://tomasp.net/blog/2017/thegamma-talk/)
- The Gamma dataviz package now available! (http://tomasp.net/blog/2017/thegamma-package/)
- Thinking the unthinkable: What we cannot think in programming (http://tomasp.net/blog/2016/thinking-unthinkable/)
- Can programming be liberated from function abstraction? (http://tomasp.net/blog/2016/no-functions/)
val it: unit = ()
|
In this example we will now also create XML in addition to consuming it.
Consider the problem of flattening a data set. Let's say you have xml data that looks like this:
[<Literal>]
let customersXmlSample = """
<Customers>
<Customer name="ACME">
<Order Number="A012345">
<OrderLine Item="widget" Quantity="1"/>
</Order>
<Order Number="A012346">
<OrderLine Item="trinket" Quantity="2"/>
</Order>
</Customer>
<Customer name="Southwind">
<Order Number="A012347">
<OrderLine Item="skyhook" Quantity="3"/>
<OrderLine Item="gizmo" Quantity="4"/>
</Order>
</Customer>
</Customers>"""
and you want to transform it into something like this:
[<Literal>]
let orderLinesXmlSample = """
<OrderLines>
<OrderLine Customer="ACME" Order="A012345" Item="widget" Quantity="1"/>
<OrderLine Customer="ACME" Order="A012346" Item="trinket" Quantity="2"/>
<OrderLine Customer="Southwind" Order="A012347" Item="skyhook" Quantity="3"/>
<OrderLine Customer="Southwind" Order="A012347" Item="gizmo" Quantity="4"/>
</OrderLines>"""
We'll create types from both the input and output samples and use the constructors on the types generated by the XmlProvider:
type InputXml = XmlProvider<customersXmlSample>
type OutputXml = XmlProvider<orderLinesXmlSample>
let orderLines =
OutputXml.OrderLines [|
for customer in InputXml.GetSample().Customers do
for order in customer.Orders do
for line in order.OrderLines do
yield OutputXml.OrderLine
( customer.Name,
order.Number,
line.Item,
line.Quantity ) |]
type InputXml = XmlProvider<...>
type OutputXml = XmlProvider<...>
val orderLines: XmlProvider<...>.OrderLines =
<OrderLines>
<OrderLine Customer="ACME" Order="A012345" Item="widget" Quantity="1" />
<OrderLine Customer="ACME" Order="A012346" Item="trinket" Quantity="2" />
<OrderLine Customer="Southwind" Order="A012347" Item="skyhook" Quantity="3" />
<OrderLine Customer="Southwind" Order="A012347" Item="gizmo" Quantity="4" />
</OrderLines>
|
The Schema
parameter can be used (instead of Sample
) to specify an XML schema.
The value of the parameter can be either the name of a schema file or plain text
like in the following example:
type Person = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="person">
<xs:complexType>
<xs:sequence>
<xs:element name="surname" type="xs:string"/>
<xs:element name="birthDate" type="xs:date"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>""">
let turing = Person.Parse """
<person>
<surname>Turing</surname>
<birthDate>1912-06-23</birthDate>
</person>
"""
printfn "%s was born in %d" turing.Surname turing.BirthDate.Year
The properties of the provided type are derived from the schema instead of being inferred from samples.
Usually a schema is not specified as plain text but stored in a file like
data/po.xsd
and the uri is set in the Schema
parameter:
type PurchaseOrder = XmlProvider<Schema="../data/po.xsd">
When the file includes other schema files, the ResolutionFolder
parameter can help locating them.
The uri may also refer to online resources:
type RssXsd = XmlProvider<Schema = "https://www.w3schools.com/xml/note.xsd">
The schema is expected to define a root element (a global element with complex type).
In case of multiple root elements:
type TwoRoots = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="root1">
<xs:complexType>
<xs:attribute name="foo" type="xs:string" use="required" />
<xs:attribute name="fow" type="xs:int" />
</xs:complexType>
</xs:element>
<xs:element name="root2">
<xs:complexType>
<xs:attribute name="bar" type="xs:string" use="required" />
<xs:attribute name="baz" type="xs:date" use="required" />
</xs:complexType>
</xs:element>
</xs:schema>
""">
the provided type has an optional property for each alternative:
let e1 = TwoRoots.Parse "<root1 foo='aa' fow='2' />"
match e1.Root1, e1.Root2 with
| Some x, None ->
printfn "Foo = %s and Fow = %A" x.Foo x.Fow
| _ -> failwith "Unexpected"
let e2 = TwoRoots.Parse "<root2 bar='aa' baz='2017-12-22' />"
match e2.Root1, e2.Root2 with
| None, Some x ->
printfn "Bar = %s and Baz = %O" x.Bar x.Baz
| _ -> failwith "Unexpected"
Foo = aa and Fow = Some 2
Bar = aa and Baz = 12/22/2017 12:00:00 AM
val e1: XmlProvider<...>.Choice = <root1 foo="aa" fow="2" />
val e2: XmlProvider<...>.Choice = <root2 bar="aa" baz="2017-12-22" />
val it: unit = ()
|
A sequence
is the most common way of structuring elements in a schema.
The following xsd defines foo
as a sequence made of an arbitrary number
of bar
elements followed by a single baz
element.
type FooSequence = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="foo">
<xs:complexType>
<xs:sequence>
<xs:element name="bar" type="xs:int" maxOccurs="unbounded" />
<xs:element name="baz" type="xs:date" minOccurs="1" />
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>""">
here a valid xml element is parsed as an instance of the provided type, with two properties corresponding to bar
and baz
elements, where the former is an array in order to hold multiple elements:
let fooSequence = FooSequence.Parse """
<foo>
<bar>42</bar>
<bar>43</bar>
<baz>1957-08-13</baz>
</foo>"""
printfn "%d" fooSequence.Bars.[0] // 42
printfn "%d" fooSequence.Bars.[1] // 43
printfn "%d" fooSequence.Baz.Year // 1957
Instead of a sequence we may have a choice
:
type FooChoice = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="foo">
<xs:complexType>
<xs:choice>
<xs:element name="bar" type="xs:int" maxOccurs="unbounded" />
<xs:element name="baz" type="xs:date" minOccurs="1" />
</xs:choice>
</xs:complexType>
</xs:element>
</xs:schema>""">
although a choice is akin to a union type in F#, the provided type still has
properties for bar
and baz
directly available on the foo
object; in fact
the properties representing alternatives in a choice are simply made optional
(notice that for arrays this is not even necessary because an array can be empty).
This decision is due to technical limitations (discriminated unions are not supported
in type providers) but also preferred because it improves discoverability:
intellisense can show both alternatives. There is a lack of precision but this is not the main goal.
let fooChoice = FooChoice.Parse """
<foo>
<baz>1957-08-13</baz>
</foo>"""
printfn "%d items" fooChoice.Bars.Length // 0 items
match fooChoice.Baz with
| Some date -> printfn "%d" date.Year // 1957
| None -> ()
0 items
1957
val fooChoice: XmlProvider<...>.Foo = <foo>
<baz>1957-08-13</baz>
</foo>
val it: unit = ()
|
Another xsd construct to model the content of an element is all
, which is used less often and
it's like a sequence where the order of elements does not matter. The corresponding provided type
in fact is essentially the same as for a sequence.
XML Schema provides various extensibility mechanisms. The following example
is a terse summary mixing substitution groups with abstract recursive definitions.
type Prop = XmlProvider<Schema = """
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="Formula" abstract="true"/>
<xs:element name="Prop" type="xs:string" substitutionGroup="Formula"/>
<xs:element name="And" substitutionGroup="Formula">
<xs:complexType>
<xs:sequence>
<xs:element ref="Formula" minOccurs="2" maxOccurs="2"/>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>""">
let formula = Prop.Parse """
<And>
<Prop>p1</Prop>
<And>
<Prop>p2</Prop>
<Prop>p3</Prop>
</And>
</And>
"""
printfn "%s" formula.Props.[0] // p1
printfn "%s" formula.Ands.[0].Props.[0] // p2
printfn "%s" formula.Ands.[0].Props.[1] // p3
p1
p2
p3
type Prop = XmlProvider<...>
val formula: XmlProvider<...>.And =
<And>
<Prop>p1</Prop>
<And>
<Prop>p2</Prop>
<Prop>p3</Prop>
</And>
</And>
val it: unit = ()
|
Substitution groups are like choices, and the type provider produces an optional
property for each alternative.
The GetSchema
method on the generated type returns an instance
of System.Xml.Schema.XmlSchemaSet
that can be used to validate documents:
open System.Xml.Schema
let schema = Person.GetSchema()
turing.XElement.Document.Validate(schema, validationEventHandler = null)
The Validate
method accepts a callback to handle validation issues;
passing null
will turn validation errors into exceptions.
There are overloads to allow other effects (for example setting default values
by enabling the population of the XML tree with the post-schema-validation infoset;
for details see the documentation).
The XML Type Provider supports most XSD features.
Anyway the XML Schema specification is rich and complex and also provides a
fair degree of openness
which may be difficult to handle in
data binding tools; but in FSharp.Data, when providing typed views on elements becomes too challenging
(take for example wildcards) the underlying XElement
is still available.
An important design decision is to focus on elements and not on complex types; while the latter
may be valuable in schema design, our goal is simply to obtain an easy and safe way to access xml data.
In other words the provided types are not intended for domain modeling (it's one of the very few cases
where optional properties are preferred to sum types).
Hence, we do not provide types corresponding to complex types in a schema but only corresponding
to elements (of course the underlying complex types still affect the shape of the provided types
but this happens only implicitly).
Focusing on element shapes let us generate a type that should be essentially the same as one
inferred from a significant set of valid samples. This allows a smooth transition (replacing Sample
with Schema
)
when a schema becomes available.
Multiple items
namespace FSharp
--------------------
namespace Microsoft.FSharp
Multiple items
namespace FSharp.Data
--------------------
namespace Microsoft.FSharp.Data
type Author = XmlProvider<...>
type XmlProvider
<summary>Typed representation of a XML file.</summary>
<param name='Sample'>Location of a XML sample file or a string containing a sample XML document.</param>
<param name='SampleIsList'>If true, the children of the root in the sample document represent individual samples for the inference.</param>
<param name='Global'>If true, the inference unifies all XML elements with the same name.</param>
<param name='Culture'>The culture used for parsing numbers and dates. Defaults to the invariant culture.</param>
<param name='Encoding'>The encoding used to read the sample. You can specify either the character set name or the codepage number. Defaults to UTF8 for files, and to ISO-8859-1 the for HTTP requests, unless <c>charset</c> is specified in the <c>Content-Type</c> response header.</param>
<param name='ResolutionFolder'>A directory that is used when resolving relative file references (at design time and in hosted execution).</param>
<param name='EmbeddedResource'>When specified, the type provider first attempts to load the sample from the specified resource
(e.g. 'MyCompany.MyAssembly, resource_name.xml'). This is useful when exposing types generated by the type provider.</param>
<param name='InferTypesFromValues'>If true, turns on additional type inference from values.
(e.g. type inference infers string values such as "123" as ints and values constrained to 0 and 1 as booleans. The XmlProvider also infers string values as JSON.)</param>
<param name='Schema'>Location of a schema file or a string containing xsd.</param>
val sample: XmlProvider<...>.Author
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.Author
Parses the specified XML string
val printfn: format: Printf.TextWriterFormat<'T> -> 'T
<summary>Print to <c>stdout</c> using the given format, and add a newline.</summary>
<param name="format">The formatter.</param>
<returns>The formatted result.</returns>
<example>See <c>Printf.printfn</c> (link: <see cref="M:Microsoft.FSharp.Core.PrintfModule.PrintFormatLine``1" />) for examples.</example>
property XmlProvider<...>.Author.Name: string with get
property XmlProvider<...>.Author.Born: int with get
type AuthorAlt = XmlProvider<...>
val doc: string
val sampleAlt: XmlProvider<...>.Author
type Detailed = XmlProvider<...>
val info: XmlProvider<...>.Author
property XmlProvider<...>.Author.Name: XmlProvider<...>.Name with get
property XmlProvider<...>.Name.Value: string with get
property XmlProvider<...>.Name.Full: bool with get
type Test = XmlProvider<...>
val v: int
XmlProvider<...>.GetSample() : XmlProvider<...>.Root
val authors: string
Multiple items
type LiteralAttribute =
inherit Attribute
new: unit -> LiteralAttribute
<summary>Adding this attribute to a value causes it to be compiled as a CLI constant literal.</summary>
<category>Attributes</category>
--------------------
new: unit -> LiteralAttribute
[<Literal>]
val ResolutionFolder: string = "D:\a\FSharp.Data\FSharp.Data\docs\library"
type Authors = XmlProvider<...>
val topic: XmlProvider<...>.Authors
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.Authors
Parses the specified XML string
property XmlProvider<...>.Authors.Topic: string with get
val author: XmlProvider<...>.Author
property XmlProvider<...>.Authors.Authors: XmlProvider<...>.Author[] with get
val printf: format: Printf.TextWriterFormat<'T> -> 'T
<summary>Print to <c>stdout</c> using the given format.</summary>
<param name="format">The formatter.</param>
<returns>The formatted result.</returns>
<example>See <c>Printf.printf</c> (link: <see cref="M:Microsoft.FSharp.Core.PrintfModule.PrintFormat``1" />) for examples.</example>
property XmlProvider<...>.Author.Born: Option<int> with get
module Option
from Microsoft.FSharp.Core
<summary>Contains operations for working with options.</summary>
<category>Options</category>
val iter: action: ('T -> unit) -> option: 'T option -> unit
<summary><c>iter f inp</c> executes <c>match inp with None -> () | Some x -> f x</c>.</summary>
<param name="action">A function to apply to the option value.</param>
<param name="option">The input option.</param>
<example id="iter-1"><code lang="fsharp">
None |> Option.iter (printfn "%s") // does nothing
Some "Hello world" |> Option.iter (printfn "%s") // prints "Hello world"
</code></example>
Multiple items
type Html = XmlProvider<...>
--------------------
type HtmlAttribute =
private | HtmlAttribute of name: string * value: string
static member New: name: string * value: string -> HtmlAttribute
<summary>Represents an HTML attribute. The name is always normalized to lowercase</summary>
<namespacedoc><summary>Contains the primary types for the FSharp.Data package.</summary></namespacedoc>
val html: XmlProvider<...>.Div
XmlProvider<...>.GetSample() : XmlProvider<...>.Div
val printDiv: div: XmlProvider<...>.Div -> unit
Prints the content of a <div> element
val div: XmlProvider<...>.Div
type Div =
inherit XmlElement
new: id: Option<string> * value: Option<string> * spans: string[] * divs: Div[] -> Div + 1 overload
member Divs: Div[]
member Id: Option<string>
member Spans: string[]
member Value: Option<string>
property XmlProvider<...>.Div.Spans: string[] with get
module Seq
from Microsoft.FSharp.Collections
<summary>Contains operations for working with values of type <see cref="T:Microsoft.FSharp.Collections.seq`1" />.</summary>
val iter: action: ('T -> unit) -> source: seq<'T> -> unit
<summary>Applies the given function to each element of the collection.</summary>
<param name="action">A function to apply to each element of the sequence.</param>
<param name="source">The input sequence.</param>
<exception cref="T:System.ArgumentNullException">Thrown when the input sequence is null.</exception>
<example id="iter-1"><code lang="fsharp">
["a"; "b"; "c"] |> Seq.iter (printfn "%s")
</code>
Evaluates to <c>unit</c> and prints
<code>
a
b
c
</code>
in the console.
</example>
property XmlProvider<...>.Div.Divs: XmlProvider<...>.Div[] with get
property System.Array.Length: int with get
<summary>Gets the total number of elements in all the dimensions of the <see cref="T:System.Array" />.</summary>
<exception cref="T:System.OverflowException">The array is multidimensional and contains more than <see cref="F:System.Int32.MaxValue" /> elements.</exception>
<returns>The total number of elements in all the dimensions of the <see cref="T:System.Array" />; zero if there are no elements in the array.</returns>
property XmlProvider<...>.Div.Value: Option<string> with get
type Census = XmlProvider<...>
val data: XmlProvider<...>.CensusApi
XmlProvider<...>.Load(uri: string) : XmlProvider<...>.CensusApi
Loads XML from the specified uri
XmlProvider<...>.Load(reader: System.IO.TextReader) : XmlProvider<...>.CensusApi
Loads XML from the specified reader
XmlProvider<...>.Load(stream: System.IO.Stream) : XmlProvider<...>.CensusApi
Loads XML from the specified stream
val apiLinks: (string * string)[]
property XmlProvider<...>.CensusApi.Datasets: XmlProvider<...>.Dataset[] with get
module Array
from Microsoft.FSharp.Collections
<summary>Contains operations for working with arrays.</summary>
<remarks>
See also <a href="https://docs.microsoft.com/dotnet/fsharp/language-reference/arrays">F# Language Guide - Arrays</a>.
</remarks>
val map: mapping: ('T -> 'U) -> array: 'T[] -> 'U[]
<summary>Builds a new array whose elements are the results of applying the given function
to each of the elements of the array.</summary>
<param name="mapping">The function to transform elements of the array.</param>
<param name="array">The input array.</param>
<returns>The array of transformed elements.</returns>
<exception cref="T:System.ArgumentNullException">Thrown when the input array is null.</exception>
<example id="map-1"><code lang="fsharp">
let inputs = [| "a"; "bbb"; "cc" |]
inputs |> Array.map (fun x -> x.Length)
</code>
Evaluates to <c>[| 1; 3; 2 |]</c></example>
val ds: XmlProvider<...>.Dataset
property XmlProvider<...>.Dataset.Title: string with get
property XmlProvider<...>.Dataset.Distribution: XmlProvider<...>.Distribution with get
property XmlProvider<...>.Distribution.AccessUrl: string with get
val truncate: count: int -> array: 'T[] -> 'T[]
<summary>Returns at most N elements in a new array.</summary>
<param name="count">The maximum number of items to return.</param>
<param name="array">The input array.</param>
<returns>The result array.</returns>
<exception cref="T:System.ArgumentNullException">Thrown when the input array is null.</exception>
<example id="truncate-1"><code lang="fsharp">
let inputs = [| "a"; "b"; "c"; "d" |]
inputs |> Array.truncate 2
</code>
Evaluates to <c>[| "a"; "b" |]</c></example>
<example id="truncate-2"><code lang="fsharp">
let inputs = [| "a"; "b"; "c"; "d" |]
inputs |> Array.truncate 6
</code>
Evaluates to <c>[| "a"; "b"; "c"; "d" |]</c></example>
<example id="truncate-3"><code lang="fsharp">
let inputs = [| "a"; "b"; "c"; "d" |]
inputs |> Array.truncate 0
</code>
Evaluates to <c>[| |]</c>.
</example>
val enqueue: title: string * apiUrl: string -> unit
val title: string
val apiUrl: string
val cacheJanitor: unit -> Async<unit>
val async: AsyncBuilder
<summary>Builds an asynchronous workflow using computation expression syntax.</summary>
<example id="async-1"><code lang="fsharp">
let sleepExample() =
async {
printfn "sleeping"
do! Async.Sleep 10
printfn "waking up"
return 6
}
sleepExample() |> Async.RunSynchronously
</code></example>
val reloadData: XmlProvider<...>.CensusApi
XmlProvider<...>.AsyncLoad(uri: string) : Async<XmlProvider<...>.CensusApi>
Loads XML from the specified uri
val iter: action: ('T -> unit) -> array: 'T[] -> unit
<summary>Applies the given function to each element of the array.</summary>
<param name="action">The function to apply.</param>
<param name="array">The input array.</param>
<exception cref="T:System.ArgumentNullException">Thrown when the input array is null.</exception>
<example id="iter-1"><code lang="fsharp">
let inputs = [| "a"; "b"; "c" |]
inputs |> Array.iter (printfn "%s")
</code>
Evaluates to <c>unit</c> and prints
<code>
a
b
c
</code>
in the console.
</example>
type Rss = XmlProvider<...>
val blog: XmlProvider<...>.Rss
XmlProvider<...>.GetSample() : XmlProvider<...>.Rss
property XmlProvider<...>.Rss.Channel: XmlProvider<...>.Channel with get
property XmlProvider<...>.Channel.Title: string with get
val item: XmlProvider<...>.Item
property XmlProvider<...>.Channel.Items: XmlProvider<...>.Item[] with get
property XmlProvider<...>.Item.Title: string with get
property XmlProvider<...>.Item.Link: string with get
[<Literal>]
val customersXmlSample: string = "
<Customers>
<Customer name="ACME">
<Order Number="A012345">
<OrderLine Item="widget" Quantity="1"/>
</Order>
<Order Number="A012346">
<OrderLine Item="trinket" Quantity="2"/>
</Order>
</Customer>
<Customer name="Southwind">
<Order Number="A012347">
<OrderLine Item="skyhook" Quantity="3"/>
<OrderLine Item="gizmo" Quantity="4"/>
</Order>
</Customer>
</Customers>"
[<Literal>]
val orderLinesXmlSample: string = "
<OrderLines>
<OrderLine Customer="ACME" Order="A012345" Item="widget" Quantity="1"/>
<OrderLine Customer="ACME" Order="A012346" Item="trinket" Quantity="2"/>
<OrderLine Customer="Southwind" Order="A012347" Item="skyhook" Quantity="3"/>
<OrderLine Customer="Southwind" Order="A012347" Item="gizmo" Quantity="4"/>
</OrderLines>"
type InputXml = XmlProvider<...>
type OutputXml = XmlProvider<...>
val orderLines: XmlProvider<...>.OrderLines
type OrderLines =
inherit XmlElement
new: orderLines: OrderLine[] -> OrderLines + 1 overload
member OrderLines: OrderLine[]
val customer: XmlProvider<...>.Customer
XmlProvider<...>.GetSample() : XmlProvider<...>.Customers
val order: XmlProvider<...>.Order
property XmlProvider<...>.Customer.Orders: XmlProvider<...>.Order[] with get
val line: XmlProvider<...>.OrderLine
property XmlProvider<...>.Order.OrderLines: XmlProvider<...>.OrderLine[] with get
type OrderLine =
inherit XmlElement
new: customer: string * order: string * item: string * quantity: int -> OrderLine + 1 overload
member Customer: string
member Item: string
member Order: string
member Quantity: int
property XmlProvider<...>.Customer.Name: string with get
property XmlProvider<...>.Order.Number: string with get
property XmlProvider<...>.OrderLine.Item: string with get
property XmlProvider<...>.OrderLine.Quantity: int with get
type Person = XmlProvider<...>
val turing: XmlProvider<...>.Person
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.Person
Parses the specified XSD string
property XmlProvider<...>.Person.Surname: string with get
property XmlProvider<...>.Person.BirthDate: System.DateTime with get
property System.DateTime.Year: int with get
<summary>Gets the year component of the date represented by this instance.</summary>
<returns>The year, between 1 and 9999.</returns>
type PurchaseOrder = XmlProvider<...>
type RssXsd = XmlProvider<...>
type TwoRoots = XmlProvider<...>
val e1: XmlProvider<...>.Choice
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.Choice
Parses the specified XSD string
property XmlProvider<...>.Choice.Root1: Option<XmlProvider<...>.Root1> with get
property XmlProvider<...>.Choice.Root2: Option<XmlProvider<...>.Root2> with get
union case Option.Some: Value: 'T -> Option<'T>
<summary>The representation of "Value of type 'T"</summary>
<param name="Value">The input value.</param>
<returns>An option representing the value.</returns>
val x: XmlProvider<...>.Root1
union case Option.None: Option<'T>
<summary>The representation of "No value"</summary>
property XmlProvider<...>.Root1.Foo: string with get
property XmlProvider<...>.Root1.Fow: Option<int> with get
val failwith: message: string -> 'T
<summary>Throw a <see cref="T:System.Exception" /> exception.</summary>
<param name="message">The exception message.</param>
<returns>The result value.</returns>
<example id="failwith-example"><code lang="fsharp">
let failingFunction() =
failwith "Oh no" // Throws an exception
true // Never reaches this
failingFunction() // Throws a System.Exception
</code></example>
val e2: XmlProvider<...>.Choice
val x: XmlProvider<...>.Root2
property XmlProvider<...>.Root2.Bar: string with get
property XmlProvider<...>.Root2.Baz: System.DateTime with get
type FooSequence = XmlProvider<...>
val fooSequence: XmlProvider<...>.Foo
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.Foo
Parses the specified XSD string
property XmlProvider<...>.Foo.Bars: int[] with get
property XmlProvider<...>.Foo.Baz: System.DateTime with get
type FooChoice = XmlProvider<...>
val fooChoice: XmlProvider<...>.Foo
property XmlProvider<...>.Foo.Baz: Option<System.DateTime> with get
val date: System.DateTime
type Prop = XmlProvider<...>
val formula: XmlProvider<...>.And
XmlProvider<...>.Parse(text: string) : XmlProvider<...>.And
Parses the specified XSD string
property XmlProvider<...>.And.Props: string[] with get
property XmlProvider<...>.And.Ands: XmlProvider<...>.And[] with get
namespace System
namespace System.Xml
namespace System.Xml.Schema
val schema: XmlSchemaSet
XmlProvider<...>.GetSchema() : XmlSchemaSet
Runtime.BaseTypes.XmlElement.XElement: System.Xml.Linq.XElement
property System.Xml.Linq.XObject.Document: System.Xml.Linq.XDocument with get
<summary>Gets the <see cref="T:System.Xml.Linq.XDocument" /> for this <see cref="T:System.Xml.Linq.XObject" />.</summary>
<returns>The <see cref="T:System.Xml.Linq.XDocument" /> for this <see cref="T:System.Xml.Linq.XObject" />.</returns>
(extension) System.Xml.Linq.XDocument.Validate(schemas: XmlSchemaSet, validationEventHandler: ValidationEventHandler) : unit
(extension) System.Xml.Linq.XDocument.Validate(schemas: XmlSchemaSet, validationEventHandler: ValidationEventHandler, addSchemaInfo: bool) : unit