How do you add listener to an existing listener object?

This doesn't work:

Models.buttons.Del = Ext.extend(Ext.Button, {
    ,text: 'Del'
    ,listeners: {
       开发者_如何学C load: function() {
        },
        ,click: function() {
        }
    }
});

Models.buttons.Add = Ext.extend(Models.buttons.Del, {
    ,text: 'Add'
    ,listeners: {
        ,click: function() {
        }
    }
});

load() event be lost in Add object.

---

you can use superclass to not to lose those methods. by doing this, you can also extend methods.

Models.buttons.Del = Ext.extend(Ext.Button, {
    ,text: 'Del'
    ,listeners: {
        load: function() {
        },
        ,click: function() {
        }
    }
});
Models.buttons.Add = Ext.extend(Models.buttons.Del, {
    ,text: 'Add'
    ,listeners: {
        load: function() {
            Models.buttons.Add.superclass.load.call(this);
        },
        ,click: function() {
        }
    }
});