Class Ember.View

Ember.View is the class in Ember responsible for encapsulating templates of HTML content, combining templates with data to render as sections of a page's DOM, and registering and responding to user-initiated events.

HTML Tag

The default HTML tag name used for a view's DOM representation is div. This can be customized by setting the tagName property. The following view class:

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ParagraphView = Ember.View.extend({
  tagName: 'em'
});

Would result in instances with the following HTML:

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<em id="ember1" class="ember-view"></em>

HTML class Attribute

The HTML class attribute of a view's tag can be set by providing a classNames property that is set to an array of strings:

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MyView = Ember.View.extend({
  classNames: ['my-class', 'my-other-class']
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view my-class my-other-class"></div>

class attribute values can also be set by providing a classNameBindings property set to an array of properties names for the view. The return value of these properties will be added as part of the value for the view's class attribute. These properties can be computed properties:

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MyView = Ember.View.extend({
  classNameBindings: ['propertyA', 'propertyB'],
  propertyA: 'from-a',
  propertyB: Ember.computed(function() {
    if (someLogic) { return 'from-b'; }
  })
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view from-a from-b"></div>

If the value of a class name binding returns a boolean the property name itself will be used as the class name if the property is true. The class name will not be added if the value is false or undefined.

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MyView = Ember.View.extend({
  classNameBindings: ['hovered'],
  hovered: true
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view hovered"></div>

When using boolean class name bindings you can supply a string value other than the property name for use as the class HTML attribute by appending the preferred value after a ":" character when defining the binding:

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MyView = Ember.View.extend({
  classNameBindings: ['awesome:so-very-cool'],
  awesome: true
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view so-very-cool"></div>

Boolean value class name bindings whose property names are in a camelCase-style format will be converted to a dasherized format:

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MyView = Ember.View.extend({
  classNameBindings: ['isUrgent'],
  isUrgent: true
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view is-urgent"></div>

Class name bindings can also refer to object values that are found by traversing a path relative to the view itself:

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MyView = Ember.View.extend({
  classNameBindings: ['messages.empty']
  messages: Ember.Object.create({
    empty: true
  })
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view empty"></div>

If you want to add a class name for a property which evaluates to true and and a different class name if it evaluates to false, you can pass a binding like this:

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// Applies 'enabled' class when isEnabled is true and 'disabled' when isEnabled is false
Ember.View.extend({
  classNameBindings: ['isEnabled:enabled:disabled']
  isEnabled: true
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view enabled"></div>

When isEnabled is false, the resulting HTML representation looks like this:

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<div id="ember1" class="ember-view disabled"></div>

This syntax offers the convenience to add a class if a property is false:

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// Applies no class when isEnabled is true and class 'disabled' when isEnabled is false
Ember.View.extend({
  classNameBindings: ['isEnabled::disabled']
  isEnabled: true
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view"></div>

When the isEnabled property on the view is set to false, it will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view disabled"></div>

Updates to the value of a class name binding will result in automatic update of the HTML class attribute in the view's rendered HTML representation. If the value becomes false or undefined the class name will be removed.

Both classNames and classNameBindings are concatenated properties. See Ember.Object documentation for more information about concatenated properties.

HTML Attributes

The HTML attribute section of a view's tag can be set by providing an attributeBindings property set to an array of property names on the view. The return value of these properties will be used as the value of the view's HTML associated attribute:

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AnchorView = Ember.View.extend({
  tagName: 'a',
  attributeBindings: ['href'],
  href: 'http://google.com'
});

Will result in view instances with an HTML representation of:

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<a id="ember1" class="ember-view" href="http://google.com"></a>

One property can be mapped on to another by placing a ":" between the source property and the destination property:

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AnchorView = Ember.View.extend({
  tagName: 'a',
  attributeBindings: ['url:href'],
  url: 'http://google.com'
});

Will result in view instances with an HTML representation of:

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<a id="ember1" class="ember-view" href="http://google.com"></a>

Namespaced attributes (e.g. xlink:href) are supported, but have to be mapped, since : is not a valid character for properties in Javascript:

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UseView = Ember.View.extend({
  tagName: 'use',
  attributeBindings: ['xlinkHref:xlink:href'],
  xlinkHref: '#triangle'
});

Will result in view instances with an HTML representation of:

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<use xlink:href="#triangle"></use>

If the return value of an attributeBindings monitored property is a boolean the attribute will be present or absent depending on the value:

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MyTextInput = Ember.View.extend({
  tagName: 'input',
  attributeBindings: ['disabled'],
  disabled: false
});

Will result in a view instance with an HTML representation of:

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<input id="ember1" class="ember-view" />

attributeBindings can refer to computed properties:

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MyTextInput = Ember.View.extend({
  tagName: 'input',
  attributeBindings: ['disabled'],
  disabled: Ember.computed(function() {
    if (someLogic) {
      return true;
    } else {
      return false;
    }
  })
});

To prevent setting an attribute altogether, use null or undefined as the return value of the attributeBindings monitored property:

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MyTextInput = Ember.View.extend({
  tagName: 'form',
  attributeBindings: ['novalidate'],
  novalidate: null
});

Updates to the property of an attribute binding will result in automatic update of the HTML attribute in the view's rendered HTML representation.

attributeBindings is a concatenated property. See Ember.Object documentation for more information about concatenated properties.

Layouts

Views can have a secondary template that wraps their main template. Like primary templates, layouts can be any function that accepts an optional context parameter and returns a string of HTML that will be inserted inside view's tag. Views whose HTML element is self closing (e.g. <input />) cannot have a layout and this property will be ignored.

Most typically in Ember a layout will be a compiled template.

A view's layout can be set directly with the layout property or reference an existing template by name with the layoutName property.

A template used as a layout must contain a single use of the {{yield}} helper. The HTML contents of a view's rendered template will be inserted at this location:

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AViewWithLayout = Ember.View.extend({
  layout: Ember.HTMLBars.compile("<div class='my-decorative-class'>{{yield}}</div>"),
  template: Ember.HTMLBars.compile("I got wrapped")
});

Will result in view instances with an HTML representation of:

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<div id="ember1" class="ember-view">
  <div class="my-decorative-class">
    I got wrapped
  </div>
</div>

See Ember.Templates.helpers.yield for more information.

Responding to Browser Events

Views can respond to user-initiated events in one of three ways: method implementation, through an event manager, and through {{action}} helper use in their template or layout.

Method Implementation

Views can respond to user-initiated events by implementing a method that matches the event name. A jQuery.Event object will be passed as the argument to this method.

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AView = Ember.View.extend({
  click: function(event) {
    // will be called when an instance's
    // rendered element is clicked
  }
});

Event Managers

Views can define an object as their eventManager property. This object can then implement methods that match the desired event names. Matching events that occur on the view's rendered HTML or the rendered HTML of any of its DOM descendants will trigger this method. A jQuery.Event object will be passed as the first argument to the method and an Ember.View object as the second. The Ember.View will be the view whose rendered HTML was interacted with. This may be the view with the eventManager property or one of its descendant views.

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AView = Ember.View.extend({
  eventManager: Ember.Object.create({
    doubleClick: function(event, view) {
      // will be called when an instance's
      // rendered element or any rendering
      // of this view's descendant
      // elements is clicked
    }
  })
});

An event defined for an event manager takes precedence over events of the same name handled through methods on the view.

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AView = Ember.View.extend({
  mouseEnter: function(event) {
    // will never trigger.
  },
  eventManager: Ember.Object.create({
    mouseEnter: function(event, view) {
      // takes precedence over AView#mouseEnter
    }
  })
});

Similarly a view's event manager will take precedence for events of any views rendered as a descendant. A method name that matches an event name will not be called if the view instance was rendered inside the HTML representation of a view that has an eventManager property defined that handles events of the name. Events not handled by the event manager will still trigger method calls on the descendant.

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var App = Ember.Application.create();
App.OuterView = Ember.View.extend({
  template: Ember.HTMLBars.compile("outer {{#view 'inner'}}inner{{/view}} outer"),
  eventManager: Ember.Object.create({
    mouseEnter: function(event, view) {
      // view might be instance of either
      // OuterView or InnerView depending on
      // where on the page the user interaction occurred
    }
  })
});

App.InnerView = Ember.View.extend({
  click: function(event) {
    // will be called if rendered inside
    // an OuterView because OuterView's
    // eventManager doesn't handle click events
  },
  mouseEnter: function(event) {
    // will never be called if rendered inside
    // an OuterView.
  }
});

{{action}} Helper

See Ember.Templates.helpers.action.

Event Names

All of the event handling approaches described above respond to the same set of events. The names of the built-in events are listed below. (The hash of built-in events exists in Ember.EventDispatcher.) Additional, custom events can be registered by using Ember.Application.customEvents.

Touch events:

• touchStart
• touchMove
• touchEnd
• touchCancel

Keyboard events

• keyDown
• keyUp
• keyPress

Mouse events

• mouseDown
• mouseUp
• contextMenu
• click
• doubleClick
• mouseMove
• focusIn
• focusOut
• mouseEnter
• mouseLeave

Form events:

• submit
• change
• focusIn
• focusOut
• input

HTML5 drag and drop events:

• dragStart
• drag
• dragEnter
• dragLeave
• dragOver
• dragEnd
• drop