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How do I reference an instance of a custom class inside a custom function defined within the class?

I've extended a class through ExtJS4's class extension "mechanism", and I've a custom event handler that will be called when something is triggered, and I want to collapse the Panel when something is fired.

However, in the event handler of the Reactor class below, "this" references EventTriggerer (The firer of the event) instead of the instance of the Reactor. How do I reference the instance of the EventReactor inside a custom function?

Thanks! DashK

Ext.define('EventReactor', {
    extend: 'Ext.panel.Panel',
    onSomething: function(data) {
        // ERROR
        // this.collapse is undefined. "this" actually references EventTriggerer
        this.collapse();
    }
});

Ext.define('EventTriggerer', {
    extend: 'Ext.util.Observable',
    singleton: true,
    constructor: function() {
        this.addEvents({
        "changedView" : true
    });
},
doSomething: function() {
    // Do some stuff
    this.fireEvent("doneSomething", data);
    }
});

...

// Here's how the listeners are added
var er = Ext.create('EventReactor');
EventTriggerer.addListener("doneSomething", er.onSomething);

// Here's how the event is triggered.
er.doSomething();

How do I reference an instance of a custom class inside a custom function defined within the class?

I've extended a class through ExtJS4's class extension "mechanism", and I've a custom event handler that will be called when something is triggered, and I want to collapse the Panel when something is fired.

However, in the event handler of the Reactor class below, "this" references EventTriggerer (The firer of the event) instead of the instance of the Reactor. How do I reference the instance of the EventReactor inside a custom function?

Thanks! DashK

Ext.define('EventReactor', {
    extend: 'Ext.panel.Panel',
    onSomething: function(data) {
        // ERROR
        // this.collapse is undefined. "this" actually references EventTriggerer
        this.collapse();
    }
});

Ext.define('EventTriggerer', {
    extend: 'Ext.util.Observable',
    singleton: true,
    constructor: function() {
        this.addEvents({
        "changedView" : true
    });
},
doSomething: function() {
    // Do some stuff
    this.fireEvent("doneSomething", data);
    }
});

...

// Here's how the listeners are added
var er = Ext.create('EventReactor');
EventTriggerer.addListener("doneSomething", er.onSomething);

// Here's how the event is triggered.
er.doSomething();

• javascript
• scope
• extjs4

Share Improve this question Follow edited Jun 22, 2011 at 15:06 JamesHalsall 13.5k44 gold badges4343 silver badges6767 bronze badges asked Jun 22, 2011 at 14:23 DashKDashK 2,68011 gold badge2222 silver badges2828 bronze badges

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2 Answers 2

Sorted by: Reset to default 9

You should create a nested scope to store "this" during constructor execution:

Ext.define('EventReactor', function() {
    var self;  // This is a variable to store "this"

    return {
        extend: 'Ext.panel.Panel',

        constructor: function() {
            self = this;  // Here you store "this" in the closure
            self.callParent(arguments);
        },

        onSomething: function(data) {
            // ERROR
            // this.collapse is undefined. "this" actually references EventTriggerer
            // this.collapse();

            // Using "self" instead of "this" => No error
            self.collapse();
        }
    };
});

Detailed information (see define method): http://docs.sencha./ext-js/4-1/#!/api/Ext

The addListener() method has an additional parameter scope that can be set to an object that bees this in the event handler.

EventTriggerer.addListener("doneSomething", er.onSomething, er);

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