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https://github.com/silverstripe/silverstripe-framework
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161 lines
6.3 KiB
Markdown
161 lines
6.3 KiB
Markdown
title: Formatting, Modifying and Casting Variables
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summary: Information on casting, security, modifying data before it's displayed to the user and how to format data within the template.
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# Formatting and Casting
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All objects that are being rendered in a template should be a [api:ViewableData] instance such as `DataObject`,
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`DBField` or `Controller`. From these objects, the template can include any method from the object in
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[scope](syntax#scope).
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For instance, if we provide a [api:HtmlText] instance to the template we can call the `FirstParagraph` method. This will
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output the result of the [api:HtmlText::FirstParagraph()] method to the template.
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**mysite/code/Page.ss**
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:::ss
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$Content.FirstParagraph
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<!-- returns the result of HtmlText::FirstParagragh() -->
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$LastEdited.Format("d/m/Y")
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<!-- returns the result of SS_Datetime::Format("d/m/Y") -->
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Any public method from the object in scope can be called within the template. If that method returns another
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`ViewableData` instance, you can chain the method calls.
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:::ss
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$Content.FirstParagraph.NoHTML
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<!-- "First Paragraph" -->
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<p>Copyright {$Now.Year}</p>
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<!-- "Copyright 2014" -->
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<div class="$URLSegment.LowerCase">
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<!-- <div class="about-us"> -->
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<div class="notice" markdown="1">
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See the API documentation for [api:HtmlText], [api:StringField], [api:Text] for all the methods you can use to format
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your text instances. For other objects such as [api:SS_Datetime] objects see their respective API documentation pages.
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</div>
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## forTemplate
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When rendering an object to the template such as `$Me` the `forTemplate` method is called. This method can be used to
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provide default template for an object.
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**mysite/code/Page.php**
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:::php
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<?php
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class Page extends SiteTree {
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public function forTemplate() {
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return "Page: ". $this->Title;
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}
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}
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**mysite/templates/Page.ss**
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:::ss
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$Me
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<!-- returns Page: Home -->
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## Casting
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Methods which return data to the template should either return an explicit object instance describing the type of
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content that method sends back, or, provide a type in the `$casting` array for the object. When rendering that method
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to a template, SilverStripe will ensure that the object is wrapped in the correct type and values are safely escaped.
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:::php
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<?php
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class Page extends SiteTree {
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private static $casting = array(
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'MyCustomMethod' => 'HTMLText'
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);
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public function MyCustomMethod() {
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return "<h1>This is my header</h1>";
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}
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}
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When calling `$MyCustomMethod` SilverStripe now has the context that this method will contain HTML and escape the data
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accordingly.
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<div class="note" markdown="1">
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By default, all content without a type explicitly defined in a `$casting` array will be assumed to be `Text` content
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and HTML characters encoded.
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</div>
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## Escaping
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Properties are usually auto-escaped in templates to ensure consistent representation, and avoid format clashes like
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displaying un-escaped ampersands in HTML. By default, values are escaped as `XML`, which is equivalent to `HTML` for
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this purpose.
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<div class="note" markdown="1">
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There's some exceptions to this rule, see the ["security" guide](../security).
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</div>
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For every field used in templates, a casting helper will be applied. This will first check for any
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`casting` helper on your model specific to that field, and will fall back to the `default_cast` config
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in case none are specified.
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By default, `ViewableData.default_cast` is set to `Text`, which will ensure all fields have special
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characters HTML escaped by default.
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The most common casting types are:
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* `Text` Which is a plain text string, and will be safely encoded via HTML entities when placed into
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a template.
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* `Varchar` which is the same as `Text` but for single-line text that should not have line breaks.
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* `HTMLFragment` is a block of raw HTML, which should not be escaped. Take care to sanitise any HTML
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value saved into the database.
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* `HTMLText` is a `HTMLFragment`, but has shortcodes enabled. This should only be used for content
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that is modified via a TinyMCE editor, which will insert shortcodes.
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* `Int` for integers.
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* `Decimal` for floating point values.
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* `Boolean` For boolean values.
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* `Datetime` for date and time.
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See the [Model data types and casting](/developer_guides/model/data_types_and_casting) section for
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instructions on configuring your model to declare casting types for fields.
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## Escape methods in templates
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Within the template, fields can have their encoding customised at a certain level with format methods.
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See [api:DBField] for the specific implementation, but they will generally follow the below rules:
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* `$Field` with no format method supplied will correctly cast itself for the HTML template, as defined
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by the casting helper for that field. In most cases this is the best method to use for templates.
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* `$Field.XML` Will invoke `htmlentities` on special characters in the value, even if it's already
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cast as HTML.
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* `$Field.ATT` will ensure the field is XML encoded for placement inside a HTML element property.
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This will invoke `htmlentities` on the value (even if already cast as HTML) and will escape quotes.
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* `Field.JS` will cast this value as a javascript string. E.g. `var fieldVal = '$Field.JS';` can
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be used in javascript defined in templates to encode values safely.
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* `$Field.CDATA` will cast this value safely for insertion as a literal string in an XML file.
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E.g. `<element>$Field.CDATA</element>` will ensure that the `<element>` body is safely escaped
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as a string.
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<div class="warning" markdown="1">
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Note: Take care when using `.XML` on `HTMLText` fields, as this will result in double-encoded
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html. To ensure that the correct encoding is used for that field in a template, simply use
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`$Field` by itself to allow the casting helper to determine the best encoding itself.
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</div>
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## Cast summary methods
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Certain subclasses of DBField also have additional summary or manipulations methods, each of
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which can be chained in order to perform more complicated manipulations.
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For instance, The following class methods can be used in templates for the below types:
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Text / HTMLText methods:
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* `$Plain` Will convert any HTML to plain text version. For example, could be used for plain-text
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version of emails.
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* `$LimitSentences(<num>)` Will limit to the first `<num>` sentences in the content. If called on
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HTML content this will have all HTML stripped and converted to plain text.
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