Backbone trigger two methods in one event

Question

I am using Backbone and I have a view with events defined:

    ....
    events: {
        'click .search-button': 'setModelTerm',
        'change .source-select': 'setModelSourceId',
        'change .source-select': 'activateSource'
    },
    ....

I would like to trigger two methods when the event change .source-select fires. The problem is that the last entry in the event object overrides the preceding entry.
How can I trigger two methods in one event?
(I am trying to prevent writing another method that calls those two methods)

Solution 1

You can pass a wrapper function in your hash of events to call your two methods.

From http://backbonejs.org/#View-delegateEvents

Events are written in the format {"event selector": "callback"}. The callback may be either the name of a method on the view, or a direct function body.

Try

events: {
    'click .search-button': 'setModelTerm',
    'change .source-select': function(e) {
        this.setModelSourceId(e);
        this.activateSource(e);
    }
},

Solution 2

The only thing that is keeping you from adding the same event/selector pair is that events is a hash - jQuery can handle multiple bindings to the same element/event pair. Good news though, jQuery events allow you to namespace events by adding a .myNamespace suffix. Practically speaking, this produces the same results but you can generate many different keys.

var MyView = Backbone.View.extend({
  events: {
    'click.a .foo': 'doSomething',
    'click.b .foo': 'doSomethingElse'
    'click.c .foo': 'doAnotherThing', // you can choose any namespace as they are pretty much transparent.
  },

  doSomething: function() {
    // ...
  },

  doSomethingElse: function() {
    // ...
  },

  doAnotherThing: function() {
    // ...
  },
});

Solution 3

The events hash in your view is just a convenience "DSL" of sorts. Just bind your 2nd event manually inside initialize.

events: {
    'click .search-button': 'setModelTerm'
},
initialize: function () {
    _.bindAll(this);
    this.on('click .search-button', this.doAnotherThing);
}

Comments

[Naor]

I wrote it specifically! "I am trying to prevent writing another method that calls those two methods".

[nikoshr]

@Naor If you want to declare something like 'change .source-select': 'setModelSourceId activateSource', you'll have to override view.delegateEvents documentcloud.github.com/backbone/docs/… which seems slightly overkill to me

[Prasanna]

Is there any way to to give a single function for multiple events?

[nikoshr]

@Prasanna You can pass the same target function multiple times, something like events: {'event1': 'name_of_function', 'event2': 'name_of_function'} assuming name_of_function is defined on the prototype of your view

[Prasanna]

thanks but i solved it this way events : {'click #btn1,#btn2,': 'function'}

[Vic]

I don't get why backbone allows multiple events one function and not multiple functions one event...

[Kent Willis]

This is wrong. Using this.on binds to Backbone.Events mixin to the view not the DOM events. If you want to manually add DOM event callbacks, use: this.$el.on('click', '.search-button', this.doAnotherThing); which is what the events hash does behind the scenes.

[Kent Willis]

And if you want them to be undelegated with the rest of the events on undelegateEvents, add this suffix to the event name: 'click.delegateEvents' + this.cid

[Peter Lyons]

@KentWillis can you post an answer with the correct code please?

[Kent Willis]

Found a better way to solve this and posted it as an answer. But if you still want to manually add an event, do: this.$el.on('click.delegateEvents' + this.cid, '.search-button', this.doAnotherThing); in an override of the delegateEvents. Make sure to call Backbone.View.prototype.delegateEvents.call(this); at the beginning of the override. This will let the view manage this custom DOM event callback alongside the other events.

[pixelearth]

this is life-changing

[ionescho]

the unsung hero here