Class Component

$ (selector) JQuery public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:997

selector

String

a jQuery-compatible selector string

returns

JQuery

the jQuery object for the DOM node

Returns a jQuery object for this component's element. If you pass in a selector string, this method will return a jQuery object, using the current element as its buffer.

For example, calling component.$('li') will return a jQuery object containing all of the li elements inside the DOM element of this component.

Please note that jQuery integration is off by default and this feature will not work properly. To enable this feature, you can read the instructions in the jquery-integration optional feature guide.

addObserver (key, target, method, sync) Observable public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:286

key

String

The key to observe

target

Object

The target object to invoke

method

String|Function

The method to invoke

sync

Boolean

Whether the observer is sync or not

returns

Observable

Adds an observer on a property.

This is the core method used to register an observer for a property.

Once you call this method, any time the key's value is set, your observer will be notified. Note that the observers are triggered any time the value is set, regardless of whether it has actually changed. Your observer should be prepared to handle that.

There are two common invocation patterns for .addObserver():

• Passing two arguments:
  • the name of the property to observe (as a string)
  • the function to invoke (an actual function)
• Passing three arguments:
  • the name of the property to observe (as a string)
  • the target object (will be used to look up and invoke a function on)
  • the name of the function to invoke on the target object (as a string).

import Component from '@ember/component';

export default Component.extend({
  init() {
    this._super(...arguments);

    // the following are equivalent:

    // using three arguments
    this.addObserver('foo', this, 'fooDidChange');

    // using two arguments
    this.addObserver('foo', (...args) => {
      this.fooDidChange(...args);
    });
  },

  fooDidChange() {
    // your custom logic code
  }
});

Observer Methods

Observer methods have the following signature:

import Component from '@ember/component';

export default Component.extend({
  init() {
    this._super(...arguments);
    this.addObserver('foo', this, 'fooDidChange');
  },

  fooDidChange(sender, key, value, rev) {
    // your code
  }
});

The sender is the object that changed. The key is the property that changes. The value property is currently reserved and unused. The rev is the last property revision of the object when it changed, which you can use to detect if the key value has really changed or not.

Usually you will not need the value or revision parameters at the end. In this case, it is common to write observer methods that take only a sender and key value as parameters or, if you aren't interested in any of these values, to write an observer that has no parameters at all.

cacheFor (keyName) Object public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:487

keyName

String

returns

Object

The cached value of the computed property, if any

Returns the cached value of a computed property, if it exists. This allows you to inspect the value of a computed property without accidentally invoking it if it is intended to be generated lazily.

decrementProperty (keyName, decrement) Number public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:448

keyName

String

The name of the property to decrement

decrement

Number

The amount to decrement by. Defaults to 1

returns

Number

The new property value

Set the value of a property to the current value minus some amount.

player.decrementProperty('lives');
orc.decrementProperty('health', 5);

destroy EmberObject public

Inherited from CoreObject packages/@ember/-internals/runtime/lib/system/core_object.js:511

returns

EmberObject

receiver

Destroys an object by setting the isDestroyed flag and removing its metadata, which effectively destroys observers and bindings.

If you try to set a property on a destroyed object, an exception will be raised.

Note that destruction is scheduled for the end of the run loop and does not happen immediately. It will set an isDestroying flag immediately.

didReceiveAttrs public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:874

Available since v1.13.0

Called when the attributes passed into the component have been updated. Called both during the initial render of a container and during a rerender. Can be used in place of an observer; code placed here will be executed every time any attribute updates.

didRender public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:895

Available since v1.13.0

Called after a component has been rendered, both on initial render and in subsequent rerenders.

didUpdate public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:963

Available since v1.13.0

Called when the component has updated and rerendered itself. Called only during a rerender, not during an initial render.

didUpdateAttrs public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:929

Available since v1.13.0

Called when the attributes passed into the component have been changed. Called only during a rerender, not during an initial render.

get (keyName) Object public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:93

keyName

String

The property to retrieve

returns

Object

The property value or undefined.

Retrieves the value of a property from the object.

This method is usually similar to using object[keyName] or object.keyName, however it supports both computed properties and the unknownProperty handler.

Because get unifies the syntax for accessing all these kinds of properties, it can make many refactorings easier, such as replacing a simple property with a computed property, or vice versa.

Computed Properties

Computed properties are methods defined with the property modifier declared at the end, such as:

import { computed } from '@ember/object';

fullName: computed('firstName', 'lastName', function() {
  return this.get('firstName') + ' ' + this.get('lastName');
})

When you call get on a computed property, the function will be called and the return value will be returned instead of the function itself.

Unknown Properties

Likewise, if you try to call get on a property whose value is undefined, the unknownProperty() method will be called on the object. If this method returns any value other than undefined, it will be returned instead. This allows you to implement "virtual" properties that are not defined upfront.

getProperties (list) Object public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:138

list

String...|Array

of keys to get

returns

Object

To get the values of multiple properties at once, call getProperties with a list of strings or an array:

record.getProperties('firstName', 'lastName', 'zipCode');
// { firstName: 'John', lastName: 'Doe', zipCode: '10011' }

is equivalent to:

record.getProperties(['firstName', 'lastName', 'zipCode']);
// { firstName: 'John', lastName: 'Doe', zipCode: '10011' }

has (name) Boolean public

Inherited from Evented packages/@ember/-internals/runtime/lib/mixins/evented.js:139

name

String

The name of the event

returns

Boolean

does the object have a subscription for event

Checks to see if object has any subscriptions for named event.

incrementProperty (keyName, increment) Number public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:426

keyName

String

The name of the property to increment

increment

Number

The amount to increment by. Defaults to 1

returns

Number

The new property value

Set the value of a property to the current value plus some amount.

person.incrementProperty('age');
team.incrementProperty('score', 2);

init public

Inherited from CoreObject packages/@ember/-internals/runtime/lib/system/core_object.js:292

An overridable method called when objects are instantiated. By default, does nothing unless it is overridden during class definition.

Example:

import EmberObject from '@ember/object';

const Person = EmberObject.extend({
  init() {
    alert(`Name is ${this.get('name')}`);
  }
});

let steve = Person.create({
  name: 'Steve'
});

// alerts 'Name is Steve'.

NOTE: If you do override init for a framework class like Component from @ember/component, be sure to call this._super(...arguments) in your init declaration! If you don't, Ember may not have an opportunity to do important setup work, and you'll see strange behavior in your application.

notifyPropertyChange (keyName) Observable public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:268

keyName

String

The property key to be notified about.

returns

Observable

Notify the observer system that a property has just changed.

Sometimes you need to change a value directly or indirectly without actually calling get() or set() on it. In this case, you can use this method instead. Calling this method will notify all observers that the property has potentially changed value.

off (name, target, method) public

Inherited from Evented packages/@ember/-internals/runtime/lib/mixins/evented.js:124

name

String

The name of the event

target

Object

The target of the subscription

method

Function|String

The function or the name of a function of the subscription

returns

this

Cancels subscription for given name, target, and method.

on (name, target, method) public

Inherited from Evented packages/@ember/-internals/runtime/lib/mixins/evented.js:54

name

String

The name of the event

target

Object

The "this" binding for the callback

method

Function|String

A function or the name of a function to be called on `target`

returns

this

Subscribes to a named event with given function.

person.on('didLoad', function() {
  // fired once the person has loaded
});

An optional target can be passed in as the 2nd argument that will be set as the "this" for the callback. This is a good way to give your function access to the object triggering the event. When the target parameter is used the callback method becomes the third argument.

one (name, target, method) public

Inherited from Evented packages/@ember/-internals/runtime/lib/mixins/evented.js:80

name

String

The name of the event

target

Object

The "this" binding for the callback

method

Function|String

A function or the name of a function to be called on `target`

returns

this

Subscribes a function to a named event and then cancels the subscription after the first time the event is triggered. It is good to use one when you only care about the first time an event has taken place.

This function takes an optional 2nd argument that will become the "this" value for the callback. When the target parameter is used the callback method becomes the third argument.

readDOMAttr (name) public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:747

name

String

the name of the attribute

returns

String

Normally, Ember's component model is "write-only". The component takes a bunch of attributes that it got passed in, and uses them to render its template.

One nice thing about this model is that if you try to set a value to the same thing as last time, Ember (through HTMLBars) will avoid doing any work on the DOM.

This is not just a performance optimization. If an attribute has not changed, it is important not to clobber the element's "hidden state". For example, if you set an input's value to the same value as before, it will clobber selection state and cursor position. In other words, setting an attribute is not always idempotent.

This method provides a way to read an element's attribute and also update the last value Ember knows about at the same time. This makes setting an attribute idempotent.

In particular, what this means is that if you get an <input> element's value attribute and then re-render the template with the same value, it will avoid clobbering the cursor and selection position. Since most attribute sets are idempotent in the browser, you typically can get away with reading attributes using jQuery, but the most reliable way to do so is through this method.

removeObserver (key, target, method, sync) Observable public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:374

key

String

The key to observe

target

Object

The target object to invoke

method

String|Function

The method to invoke

sync

Boolean

Whether the observer is async or not

returns

Observable

Remove an observer you have previously registered on this object. Pass the same key, target, and method you passed to addObserver() and your target will no longer receive notifications.

rerender public

Inherited from Ember.ViewMixin packages/@ember/-internals/views/lib/mixins/view_support.js:119

Renders the view again. This will work regardless of whether the view is already in the DOM or not. If the view is in the DOM, the rendering process will be deferred to give bindings a chance to synchronize.

If children were added during the rendering process using appendChild, rerender will remove them, because they will be added again if needed by the next render.

In general, if the display of your view changes, you should modify the DOM element directly instead of manually calling rerender, which can be slow.

send (actionName, context) public

Inherited from Ember.ActionHandler packages/@ember/-internals/runtime/lib/mixins/action_handler.js:167

actionName

String

The action to trigger

context

*

a context to send with the action

Triggers a named action on the ActionHandler. Any parameters supplied after the actionName string will be passed as arguments to the action target function.

If the ActionHandler has its target property set, actions may bubble to the target. Bubbling happens when an actionName can not be found in the ActionHandler's actions hash or if the action target function returns true.

Example

import Route from '@ember/routing/route';

export default Route.extend({
  actions: {
    playTheme() {
      this.send('playMusic', 'theme.mp3');
    },
    playMusic(track) {
      // ...
    }
  }
});

set (keyName, value) Object public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:163

keyName

String

The property to set

value

Object

The value to set or `null`.

returns

Object

The passed value

Sets the provided key or path to the value.

record.set("key", value);

This method is generally very similar to calling object["key"] = value or object.key = value, except that it provides support for computed properties, the setUnknownProperty() method and property observers.

Computed Properties

If you try to set a value on a key that has a computed property handler defined (see the get() method for an example), then set() will call that method, passing both the value and key instead of simply changing the value itself. This is useful for those times when you need to implement a property that is composed of one or more member properties.

Unknown Properties

If you try to set a value on a key that is undefined in the target object, then the setUnknownProperty() handler will be called instead. This gives you an opportunity to implement complex "virtual" properties that are not predefined on the object. If setUnknownProperty() returns undefined, then set() will simply set the value on the object.

Property Observers

In addition to changing the property, set() will also register a property change with the object. Unless you have placed this call inside of a beginPropertyChanges() and endPropertyChanges(), any "local" observers (i.e. observer methods declared on the same object), will be called immediately. Any "remote" observers (i.e. observer methods declared on another object) will be placed in a queue and called at a later time in a coalesced manner.

setProperties (hash) Object public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:211

hash

Object

the hash of keys and values to set

returns

Object

The passed in hash

Sets a list of properties at once. These properties are set inside a single beginPropertyChanges and endPropertyChanges batch, so observers will be buffered.

record.setProperties({ firstName: 'Charles', lastName: 'Jolley' });

toString String public

Inherited from CoreObject packages/@ember/-internals/runtime/lib/system/core_object.js:546

returns

String

string representation

Returns a string representation which attempts to provide more information than Javascript's toString typically does, in a generic way for all Ember objects.

import EmberObject from '@ember/object';

const Person = EmberObject.extend();
person = Person.create();
person.toString(); //=> "<Person:ember1024>"

If the object's class is not defined on an Ember namespace, it will indicate it is a subclass of the registered superclass:

const Student = Person.extend();
let student = Student.create();
student.toString(); //=> "<(subclass of Person):ember1025>"

If the method toStringExtension is defined, its return value will be included in the output.

const Teacher = Person.extend({
  toStringExtension() {
    return this.get('fullName');
  }
});
teacher = Teacher.create();
teacher.toString(); //=> "<Teacher:ember1026:Tom Dale>"

toggleProperty (keyName) Boolean public

Inherited from Observable packages/@ember/-internals/runtime/lib/mixins/observable.js:470

keyName

String

The name of the property to toggle

returns

Boolean

The new property value

Set the value of a boolean property to the opposite of its current value.

starship.toggleProperty('warpDriveEngaged');

trigger (name, args) public

Inherited from Evented packages/@ember/-internals/runtime/lib/mixins/evented.js:101

name

String

The name of the event

args

Object...

Optional arguments to pass on

Triggers a named event for the object. Any additional arguments will be passed as parameters to the functions that are subscribed to the event.

person.on('didEat', function(food) {
  console.log('person ate some ' + food);
});

person.trigger('didEat', 'broccoli');

// outputs: person ate some broccoli

willDestroy public

Inherited from CoreObject packages/@ember/-internals/runtime/lib/system/core_object.js:538

Override to implement teardown.

willRender public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:912

Available since v1.13.0

Called before a component has been rendered, both on initial render and in subsequent rerenders.

willUpdate public

Defined in packages/@ember/-internals/glimmer/lib/component.ts:946

Available since v1.13.0

Called when the component is about to update and rerender itself. Called only during a rerender, not during an initial render.