# Core functions

## xxf:document-id()

```
xxf:document-id() as xs:string`
```

Each time an XForms document is created, typically when a user requests a page, it is assigned a unique id.

This function returns the current XForms document (or page)'s unique id.

## xxf:evaluate-avt()

```
xxf:evaluate-avt(
    $avt-expression as xs:string
) as item()*
```

This function is similar to `saxon:evaluate()` or `xxf:evaluate()`, but instead of evaluating an XPath expression, it evaluates a string representing an attribute value template.

```markup
<xf:output
    value="
        xxf:evaluate-avt(
            '/xforms-sandbox/service/zip-zips?state-abbreviation={state}&amp;city={city}'
        )"/>
```

## xxf:format-message()

```
xxf:format-message(
    $template as xs:string, 
    $params   as item()*
) as xs:string
```

The `xxf:format-message()` function allows you to format a localized message based on a template and parameters.

* the first parameter is a template string following the syntax of the Java [MessageFormat](http://docs.oracle.com/javase/7/docs/api/java/text/MessageFormat.html) class
* the second parameter is a sequence of parameters that can be referenced from the template string

The following types are supported:

* string (the default)
* number (including currency and percent)
* date
* time

The function uses the current language as would be obtained by the `xxf:lang()` function to determine a locale.

Example with number, date, time, and string:

```markup
<xf:output
    value="
        xxf:format-message(
            'At {2,time,short} on {2,date,long}, we detected {1,number,integer} spaceships on the planet {0}.',
            (
                'Mars',
                3,
                xs:dateTime('2010-07-23T19:25:13-07:00')
            )
        )"/>
```

This produces the following output with an en-US locale:

```
At 7:25 PM on July 23, 2010, we detected 3 spaceships on the planet Mars.
```

Example including a choice:

```markup
<xf:output
    value="
        xxf:format-message(
            'There {0,choice,0#are no files|1#is one file|1&lt;are {0,number,integer} files}.',
            xs:integer(.)
        )"/>
```

This produces the following outputs, depending on the value provided:

```
There are no files.
There is one file.
There are 1,273 files.
```

*NOTE: It is important to pass dates and times as typed values. Use* `xs:dateTime()`*,* `xs:date()`*, or* `xs:time()` *if needed to convert from a string.*

## xxf:lang()

```
xxf:lang() as xs:string?
```

The `xxf:lang()` function returns the current language as specified with the `xml:lang` attribute.

The `xml:lang` value to use is determined this way:

* if the element containing the `xxf:lang()` function has an `xml:lang` attribute, that attribute is used
* otherwise, the first ancestor element of the element containing the `xxf:lang()` function that has an `xml:lang` attribute is used

`xml:lang` is supported in the following locations:

* for a static `xml:lang` value
  * on any XForms element
  * on the top-level `<xh:html>` element
* for a dynamic xml:lang value (using an AVT)
  * only on the top-level `<xh:html>` element

*NOTE:* `xml:lang` *attributes on HTML elements other than the top-level* `<xh:html>` *are ignored for the purpose of the* `xxf:lang()` *function.*

*NOTE: Format of the locale is currently restricted to the form "en" or "en-GB". Support for* [*BCP 47*](http://www.rfc-editor.org/rfc/bcp/bcp47.txt) *would be desirable.*

Example of static values:

```markup
<xf:group xml:lang="it">
    <!-- This output produces the value "it" -->
    <xf:output value="xxf:lang()"/>
    <!-- This output produces the value "zh" -->
    <xf:output value="xxf:lang()" xml:lang="zh"/>
</xf:group>
```

Example with an AVT:

```markup
<xh:html xml:lang="{instance()}">
    <xh:head>
        <xf:model id="model">
            <xf:instance id="instance">
                <lang>it</lang>
            </xf:instance>
        </xf:model>
    </xh:head>
    <xh:body>
        <xf:group>
            <!-- This output produces "it" based on the top-level AVT, which
                 contains the value stored in the instance -->
            <xf:output value="xxf:lang()"/>
            <!-- This output produces "zh" -->
            <xf:output value="xxf:lang()" xml:lang="zh"/>
        </xf:group>
    </xh:body>
</xh:html>
```

When calling the `xxf:lang()` function from an XBL component:

* `xml:lang` is first searched as described above
* if no `xml:lang` value is found in the XBL component, then the `xml:lang` value of the XBL bound element is searched

Example:

```markup
<xbl:xbl>
    <xbl:binding id="fr-foo" element="fr|foo">
        <xbl:template>
            <xf:group>
                <!-- The xml:lang value of the bound element is used -->
                <xf:output value="xxf:lang()"/>
                <!-- The xml:lang value is "zh" -->
                <xf:output value="xxf:lang()" xml:lang="zh"/>
            </xf:group>
        </xbl:template>
    </xbl:binding>
</xbl:xbl>
```

## xxf:process-template()

\[SINCE Orbeon Forms 2018.1]

```
xxf:process-template(
    $template as xs:string,
    $lang     as xs:string,
    $params   as map(*)
) as xs:string?
```

This function fills a string template with values passed separately.

* `$template`: template of the form:

  ```
    My name is {$name}. I am {$age} year-old.
  ```
* `$lang`: language for formatting of parameters
* `$params`: name → value XPath `map`

Example with `xmlns:map="http://www.w3.org/2005/xpath-functions/map"` in scope:

```
xxf:process-template(
    'My name is {$name}. I am {$age} year-old. I own $ {$amount}.',
    'en',
    map:merge(
        (
            map:entry('name',    'Marco Polo'),
            map:entry('age',     42),
            map:entry('amount',  12.99)
        )
    )
)
```

This evaluates to:

> My name is Marco Polo. I am 42 year-old. I own $ 12.99.

*NOTE: As Orbeon Forms 2018.1, parameters are formatted per Java's* `MessageFormat`*. It is expected that in the future, these values will be formatted as they are with* `xf:output`*, and possibly configurable. If the exact format is important, instead of passing* `xs:integer`*,* `xs:date`*, etc. types, format the value as an* `xs:string` *first before passing it as parameter.*

## xxf:property()

```
xxf:property($property-name as xs:string) as xs:anyAtomicType?
```

The `xxf:property()` function retrieves the value of a property defined in `properties-local.xml`.

This function returns the following:

* empty sequence if the property is not found
* `xs:string`, `xs:integer`, `xs:boolean` or `xs:anyURI` depending on the actual type of the property

```markup
<xf:setvalue ref="my-property" value="xxf:property('my.property.name')"/>
```

## xxf:r()

The purpose of this function is to automatically resolve resources by name given the current language and an XForms instance containing localized resources.

```
xxf:r($resource-name as xs:string) as xs:string?
xxf:r($resource-name as xs:string, $instance-name as xs:string) as xs:string?
```

* `$resource-name`: resource path of the form `foo.bar.baz`. The path is relative to the `resource` element corresponding to the current language in the resources instance.
* `$instance-name`: name of the resources instance. If omitted, search `orbeon-resources` and then `fr-form-resources`.

The function:

* determines the current language based on `xml:lang`attribute in scope where the function is in used
* resolves the closest relevant resources instance
  * specified instance name if present
  * `orbeon-resources` or `fr-form-resources` (for Form Runner compatibility) if absent
* uses the resource name specified to find a resource located in the resources instance, relative to the `resource` element with the matching language

Example:

```markup
<xf:instance id="orbeon-resources" xxf:readonly="true">
    <resources>
        <resource xml:lang="en"><buttons><download>Download</download></buttons></resource>
        <resource xml:lang="fr"><buttons><download>Télécharger</download></buttons></resource>
    </resources>
</xf:instance>

<xf:label value="xxf:r('buttons.download')"/>
```

\[SINCE Orbeon Forms 2018.1]

The function supports filling a template with parameters when the `$params` is supplied:

```
xxf:r(
    $resource-name as xs:string, 
    $instance-name as xs:string,
    $params        as map(*)
) as xs:string
```

In this case, the function fills the template as with the [`xxf:process-template()`](#xxf-process-template) function.

## xxf:resource-elements()

\[SINCE Orbeon Forms 2018.2]

Like `xxf:r()`, The purpose of this function is to automatically resolve resources by name given the current language and an XForms instance containing localized resources. The difference is that this function resolves to resource elements instead of resolving to a resource string.

```
xxf:resource-elements(
    $resource-name as xs:string
) as element()*

xxf:resource-elements(
    $resource-name as xs:string, 
    $instance-name as xs:string
) as element()*
```

* `$resource-name`: resource path of the form `foo.bar.baz`. The path is relative to the `resource` element corresponding to the current language in the resources instance.
* `$instance-name`: name of the resources instance. If omitted, search `fr-form-resources`.

Example:

```markup
<xf:itemset ref="xxf:resource-elements('default-always-never.item')">
    <xf:label ref="."/>
    <xf:value ref="if (@id = 0) then 'default' else if (@id = 1) then 'true' else 'false'"/>
</xf:itemset>
```

## xxf:rewrite-resource-uri()

```
xxf:rewrite-resource-uri($uri as xs:string) as xs:string
```

Rewrite a URI as an Orbeon Forms resource URI.