dojox/form/manager

Project owner:Eugene Lazutkin
since:1.3

Introduction

The form manager is designed to implement highly interactive event-driven CRUD (sub)applications. In most cases such application can be a reflection of underlying database tables, or an interface to complex calculations.

The form manager helps to do following common tasks:

  • Working with both form widgets and common HTML elements presenting the unified API regardless of underlying form elements.
  • Unified interfaces for underlying form elements:
    • Get or set values.
    • Enable or disable form fields.
    • Show or hide HTML elements.
    • Add or remove classes of all controlled elements.
  • Unified interface to enable/disable underlying form elements.
  • Processing of unified change events for underlying form elements using observers.
  • Orchestration of complex client-side validation of groups of fields. A simple form widget validation is supported automatically.
  • Orchestration of I/O.
  • Form support on the level of dijit/form/Form.

In general the form manager shields programmers and designers from dealing with specific form elements. It is quite possible for a designer to use a text input widget for some field, rearrange the HTML later changing the field to a select node, and then change it to a group of radio buttons --- all without changing a single line in the form-handling code. All event processing, value access, enable/disable functionality, and so on will continue working regardless of those changes.

Controlled elements

The form manager works with following elements (inspected on instantiation):

  • Form widgets.

    All form widgets (objects based on dijit/form/_FormWidget) are recognized automatically. A value of the name attribute of form widget is used as a unique identifier for this widget.

    Important exception: radio buttons all share the same name and grouped as a single complex widget.

  • HTML form elements.

    All HTML form elements (<input>, <select>, <textarea>, <button>`:ref:`) are recognized automatically, if `NodeMixin <dojox/form/manager/_NodeMixin>`_ is included. A value of the ``name attribute of form element is used as a unique identifier for this widget.

    Important exception: radio buttons all share the same name and grouped as a single complex widget.

  • Any node attribute of the widget itself.

    The usual source of such nodes is the data-dojo-attach-point directive of dojo/parser. Following names are ignored: domNode, containerNode, srcNodeRef, bgIframe (they are used internally by the widget machinery).

The DOM nodes of the 3rd class are not considered to be form fields automatically and will be ignored by value-related operations to prevent inefficiencies. But in some cases it is important to use such non-form elements as a read-only fields. If you want to designate a DOM node as a value field, you should do two things:

  • Use data-dojo-attach-point on such node so it'll be promoted to widget attributes.
  • Mark this node with a CSS class dojoFormValue. This class indicates that you opt-in this node as a value node.

Example:

<div data-dojo-type="dojox/form/Manager">
  <input type="checkbox" data-dojo-type="dijit/form/CheckBox" name="w01" value="w01">
  <input type="text" name="e03" value="e03">
  <span data-dojo-attach-point="n01" class="dojoFormValue">&nbsp;</span>
  <span data-dojo-attach-point="n02">test</span>
</div>

This fictitious form demonstrates following:

  • The form manager widget is created on line #1. Note that this example doesn't use the <form> tag.
  • The form widget on line #2 will be automatically recognized as a controlled element. It can be accessed as "w01".
  • The form node on line #3 will be automatically recognized as a controlled element, if node processing is added like in this example. It can be accessed as "e03".
  • The span node on line #4 will be automatically recognized as a controlled element. Its value can be read/written because it is marked with the CSS class dojoFormValue.
  • The span node on line #5 will be automatically recognized as a controlled element. Its value cannot be read/written because it is not marked with the CSS class dojoFormValue. All other operations will work as normal.

Event processing

The form manager normalizes change events on all form widgets and HTML form elements. In order to request this special event processing, add data-dojo-observer attribute to a form widget or an HTML form element. The value of data-dojo-observer is a string that lists event handler names using comma to separate them.

In a radio button group all observers are pooled together regardless of what element of the group they are attached to and attached to the whole group as the single form widget.

Observers cannot be attached to non-form elements for obvious reasons (no way to deduce the change event). Use data-dojo-attach-event for that.

An observer method is a method on the current form manager. They can be added by adding them to the form manager object using common JavaScript methods, or added dynamically with dojo/parser.

When the change event is triggered each relevant observer will be called in the context of the form manager with following parameters:

  • value --- the new value of form widget or form element.
  • name --- the name of form widget or form element. This parameter is useful when you attach the same observer to different form elements.
  • element --- the widget object for widgets, or a DOM node for form nodes. This parameter is rarely used but can be helpful for some advanced processing.
  • evt --- the original event object. This parameter is rarely used but can be helpful for some advanced processing.

Example:

<div data-dojo-type="dojox/form/Manager">
  <input type="checkbox" data-dojo-type="dijit/form/CheckBox" name="w01" value="w01" data-dojo-observer="log">
  <input type="text" name="e03" value="e03" data-dojo-observer="log,disabler">
  <span data-dojo-attach-point="n01" class="dojoFormValue">&nbsp;</span>
  <span data-dojo-attach-point="n02" data-dojo-attach-event="onclick: clicked">test</span>
  <script type="dojo/method" data-dojo-event="log" data-dojo-args="value,name">
    console.log(name, " = ", value);
  </script>
  <script type="dojo/method" data-dojo-event="disabler" data-dojo-args="value,name">
    if(value.length > 5){
      this.disable([name]);
    }
  </script>
  <script type="dojo/method" data-dojo-event="clicked">
    console.log("we got clicked!");
  </script>
</div>

We extended the previous example with observers and included required observers inline using dojo/method. Let's go over new additions line by line:

  • On line #2 we added an observer named log. It will be called on every value change of the widget "w01".
  • On line #3 we added two observers named log and disabler. They both will be called on every value change of the widget "e03".
  • On line #5 we added a simple onclick event handler named clicked. It will be called when user clicks this DOM node.
  • Lines ##6-8 define log() observer. It uses two parameters value and name ignoring the rest. When it is called it prints the name and the new value of the form widget or form node it is observing.
  • Lines ##9-13 define disabler() observer. Just like log() it uses the same two parameters. It will disable the controlled widget/node when the length of its text value exceeds 5. Note that on line #11 it uses this, which is the form manager object of that form.
  • Lines ##14-16 define a simple event handler clicked(), which doesn't use any parameters, and prints a static text.

Components

The form manager package consists of the main widget: dojox/form/Manager and a set of mixins (don't mind the leading underscore) located in /dojox/form/manager:

  • _Mixin

    The main mixin, which should be always included. It provides the initialization and handles form widgets, data-dojo-attach-point-s, and observers directly.

  • _NodeMixin

    Optional. It plugs into _Mixin extending it with new methods and ability to handle HTML form nodes.

  • _FormMixin

    Optional. Helpful when the top element of the widget is a <form>. In this case it provides onReset() and onSubmit() functionality with reasonable defaults. Additionally it provides isValid() method, which validates all form widgets individually. Essentially it mirrors dijit/form/Form.

  • _ValueMixin

    Optional. Provides a unified way to access (get/set) a value of any controlled element. Provides group-get/set functionality as well. This is one of the most useful mixins.

  • _EnableMixin

    Optional. Provides a unified way to access (get/set) an enable state of any controlled element with a group-get/set functionality as well.

  • _DisplayMixin

    Optional. Provides a unified way to access (get/set) an display state of any controlled HTML element with a group-get/set functionality as well.

  • _ClassMixin

    Optional. Provides a unified way to add/remove a CSS class on any controlled element with a group-get/set functionality as well.

You don't have to use Manager directly. In many cases it is more beneficial to add form manager mixins directly to your custom widget adding a required functionality. Think of mixins as "plugins" for other widgets.

This architecture provides for ultimate flexibility. All functionality is in mixins, and user can mix and match only necessary features conserving the downloadable bytes, if needed. Writing additional mixins is supported and actively encouraged!

Manager is a simple widget that includes all above listed mixins, and treats its body as a template. Using it you don't need to put the template in the separate file but can do it completely inline. It allows to use normal template-specific directives for dojo/parser: data-dojo-attach-point, data-dojo-attach-event, and a special directive used in the form manager: data-dojo-observer to designate methods to be called for all high-level change events on this element (a form widget or an HTML form element). You can use it as is, or as a sample code for your own custom widgets.

Please refer to documentation of individual mixins and the widget for details of their API and implementation.

Available tests

All tests are located in the dojox/form/tests/ sub-directory. They are used by developers to test the conformance, and can be used by users to see how different objects and algorithms can be used. Following tests are available (these are external links to Dojo Nightlies, which are are not set up for speed but for debugging):