从topic.subscribe的回调访问小部件

Question

I'm trying to use Dojo's pub/sub topic module as documented here . I am subscribing to an event inside a custom widget's startup() method and would like to modify the widget when the topic is triggered.

How do I access the widget from the topic.subscribe() callback? Inside the callback, this does not refer to the widget; I'm not sure what it refers to... the this object includes emit and on functions, as well as a declaredClass field that looks like "uniqName_0" .

Answer 1

You want to use dojo/_base/lang::hitch to change the scope of callback function when subscribing inside the widget method, where this refers to the widgets instance. You have a couple of options here:

1. anonymous function:

    topic.subscribe("topic/some", lang.hitch(this, function() { // your callback logic here })); 

2. the method of widget:

    topic.subscribe("topic/some", lang.hitch(this, "callbackMethod")); 

See it in action: http://jsfiddle.net/phusick/N7NGB/

Answer 2

The widget has some convenience methods that will handle the hitch as phusick describes.

In the startup method, you can write

startup: function() {
  this.inherited(arguments);

  this.subscribe('topic/some', '_onTopic');
},

_onTopic: function() {
  this.something // 'this' is the widget
}

A widget has other convenience methods

this.unsubscribe
this.connect
this.disconnect

When using the subscribe and connect methods, the unsubscribe and disconnect methods will be automatically called when the widget is destroyed.

http://dojotoolkit.org/api/dijit/_WidgetBase