AjaxUniqueTextField Example

mysite_code_dataobjects_MyDataObject.php

<?php

class MyDataObject extends DataObject
{
	public function getCMSFields()
	{
		$fields = parent::getCMSFields();

		// Place a unique value constraint MyDataObjects table, MyCode column
		$myAjax = new MyAjaxUniqueTextField('MyCode', 'My Code', 'MyCode', 'MyDataObject', "", null, null, null, $this->ID);
		$fields->replaceField('MyCode', $myAjax);
		return $fields;
	}
}

mysite_code_forms_MyAjaxUNiqueTextField.php

<?php

class MyAjaxUniqueTextField extends AjaxUniqueTextField
{

	public function __construct($name, $title, $restrictedField, $restrictedTable, $value = "", $maxLength = null, $validationURL = null, $restrictedRegex = null, $recordID = null)
	{
		// assign record                 
		$this->recordID = $recordID;

		parent::__construct($name, $title, $restrictedField, $restrictedTable, $value, $maxLength,
			$validationURL, $restrictedRegex);
	}

	public function validate($validator)
	{
    // validate against db records
		$result = DB::query(sprintf(
			"SELECT COUNT(*) FROM \"%s\" WHERE \"%s\" = '%s' AND \"ID\" != '
                        %s' ",
			$this->restrictedTable,
			$this->restrictedField,
			Convert::raw2sql($this->value),
			$this->recordID
		))->value();

		if ($result && ($result > 0)) {
			$validator->validationError($this->name,
				_t('Form.VALIDATIONNOTUNIQUE', "The value entered is not unique"));
			return false;
		}

		return true;
	}

}