Question

I am trying to get better at extending the classes of Extjs, and my evolvement have lead me to this problem:

I have extended an Ext.Panel and I want my extension to have a bottom toolbar with one button as default.

myPanel = Ext.extend(Ext.Panel, {
    method: function () {
        return 'response!';
    },

    bbar: new Ext.Toolbar({
        items:
        [
            {
                xtype: 'button',
                text: 'Hit me!',
                handler: function (button, event) {
                    alert(this.method());
                },
                scope: this
            }
        ]
    })
});

What I haven’t learnt yet is why this is not allowed. this is pointing at the global scope and not my extended panel – thus .method() is undefined inside the handler function.

Answer 1

You’re defining the bbar on the prototype rather than on a specific object.

Override initComponent and move the bbar definition inside it.

myPanel = Ext.extend(Ext.Panel, {
    method: function () {
        return 'response!';
    },

    initComponent: function() {    
        var bbar = new Ext.Toolbar({
            items:
            [
                {
                    xtype: 'button',
                    text: 'Hit me!',
                    handler: function (button, event) {
                        alert(this.method());
                    },
                    scope: this
                }
            ]
        });

        // Config object has already been applied to 'this' so properties can 
        // be overriden here or new properties (e.g. items, tools, buttons) 
        // can be added, eg:
        Ext.apply(this, {
            bbar: bbar
        });

        // Call parent (required)
        myPanel.superclass.initComponent.apply(this, arguments);

        // After parent code
        // e.g. install event handlers on rendered component
    }
});

See http://www.sencha.com/learn/Manual:Component:Extending_Ext_Components for a template you can use when extending components