NEW SearchableDropdownField

lang/en.yml

@@ -141,6 +141,10 @@ en:
     IsNullLabel: 'Is Null'
   SilverStripe\Forms\NumericField:
     VALIDATION: "'{value}' is not a number, only numbers can be accepted for this field"
+  SilverStripe\Forms\SearchableDropdownTrait:
+    SELECT: 'Select...'
+    TYPE_TO_SEARCH: 'Type to search...'
+    SELECT_OR_TYPE_TO_SEARCH: 'Select or type to search...'
   SilverStripe\Forms\TextField:
     VALIDATEMAXLENGTH: 'The value for {name} must not exceed {maxLength} characters in length'
   SilverStripe\Forms\TimeField:

src/Forms/SearchableDropdownField.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace SilverStripe\Forms;
+
+use SilverStripe\Forms\DropdownField;
+
+class SearchableDropdownField extends DropdownField
+{
+    use SearchableDropdownTrait;
+
+    // This needs to be defined on the class, not the trait, otherwise there is a PHP error
+    protected $schemaComponent = 'SearchableDropdownField';
+
+    /**
+     * @param string $name
+     * @param string $title
+     * @param DataList|ArrayList|ArrayAccess|array $source
+     * @param mixed $value
+     * @param string $labelField
+     */
+    public function __construct($name, $title = '', $source = [], $value = null, $labelField = 'Title')
+    {
+        // Note that an ancestor constructor will call $this->setSource() which will call
+        // setSource() in this class which throw an exception if $source is not a DataList
+        parent::__construct($name, $title, $source, $value);
+        $this->setLabelField($labelField);
+        $this->addExtraClass('ss-searchable-dropdown-field');
+    }
+}