mirror of
https://github.com/silverstripe/silverstripe-framework
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142 lines
3.9 KiB
Markdown
142 lines
3.9 KiB
Markdown
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# Grouping Data Object Sets
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The [api:DataObjectSet] class has a number of methods useful for grouping objects by fields. Together with sorting this
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can be used to break up long lists of data into more manageable sub-sections.
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The [api:DataObjectSet->groupBy()] method takes a field name as the single argument, and breaks the set up into a number
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of arrays, where each array contains only objects with the same value of that field. The [api:DataObjectSet->GroupedBy()]
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method builds on this and returns the same data in a template-friendly format.
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## Grouping Sets By First Letter
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This example deals with breaking up a [api:DataObjectSet] into sub-headings by the first letter.
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Let's say you have a set of Module objects, each representing a SilverStripe module, and you want to output a list of
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these in alphabetical order, with each letter as a heading; something like the following list:
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* B
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* Blog
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* C
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* CMS Workflow
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* Custom Translations
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* D
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* Database Plumber
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* ...
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The first step is to set up the basic data model, along with a method that returns the first letter of the title. This
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will be used both for grouping and for the title in the template.
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:::php
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class Module extends DataObject {
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public static $db = array(
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'Title' => 'Varchar(255)'
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);
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// ...
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/**
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* Returns the first letter of the module title, used for grouping.
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*
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* @return string
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*/
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public function getTitleFirstLetter() {
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return $this->Title[0];
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}
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}
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The next step is to create a method or variable that will contain/return all the Module objects, sorted by title. For
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this example this will be a method on the Page class.
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:::php
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class Page extends SiteTree {
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// ...
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/**
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* Returns all modules, sorted by their title.
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*
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* @return DataObjectSet
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*/
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public function getModules() {
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return DataObject::get('Module', null, '"Title"');
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}
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}
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The final step is to render this into a template. The [api:DataObjectSet->GroupedBy()] method breaks up the set into
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a number of sets, grouped by the field that is passed as the parameter. In this case, the getTitleFirstLetter method
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defined earlier is used to break them up.
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:::ss
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<h2>Modules</h2>
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<% control Modules.GroupedBy(TitleFirstLetter) %>
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<h3>$TitleFirstLetter</h3>
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<ul>
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<% control Children %>
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<li>$Title</li>
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<% end_control %>
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</ul>
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<% end_control %>
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## Grouping Sets By Month
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Grouping a set by month is a very similar process. The only difference would be to sort the records by month name, and
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then create a method on the DataObject that returns the month name, and pass that to the [api:DataObjectSet->GroupedBy()]
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call.
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Again, the first step is to create a method on the class in question that will be displayed in a list. For this example,
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a [api:DataObject] called NewsItem will be used. This will have a method which returns the month it was posted in:
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:::php
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class NewsItem extends DataObject {
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public static $db = array(
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'Title' => 'Varchar(255)',
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'Date' => 'Date'
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);
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// ...
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/**
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* Returns the month name this news item was posted in.
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*
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* @return string
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*/
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public function getMonthPosted() {
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return date('F', strtotime($this->Date));
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}
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}
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The next step is to create a method that will return all the News records that exist, sorted by month name from
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January to December. This can be accomplshed by sorting by the Date field:
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:::php
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class Page extends SiteTree {
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/**
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* Returns all news items, sorted by the month they were posted
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*
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* @return DataObjectSet
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*/
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public function getNewsItems() {
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return DataObject::get('NewsItem', null, '"Date"');
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}
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}
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The final step is the render this into the template using the [api:DataObjectSet->GroupedBy()] method.
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:::ss
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<h2>Modules</h2>
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<% control NewsItems.GroupedBy(MonthPosted) %>
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<h3>$MonthPosted</h3>
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<ul>
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<% control Children %>
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<li>$Title ($Date.Nice)</li>
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<% end_control %>
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</ul>
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<% end_control %>
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