ExtJS button handler not working - extjs

Question

My ExtJS button's handler is not invoked after clicking. Now the code looks like this.
Ext.define('EDS.view.selector.Container', {
extend: 'Ext.form.Panel',
alias : 'widget.selectorcontainer',
title: 'Selector_V2',
renderTo: 'input-div',
layout: 'fit',
height: '100%',
items: [
{
xtype: 'tabpanel',
defaults: {
bodyPadding: 10
},
}
],
buttons: [
{
text: 'Reset',
handler: function(){
console.log("Reset");
this.up('form').getForm().reset();
}
},
{
text: 'Add to constrain',
handler: this.addConstrain,
}
],
/*
* Logic for button "Add to constrain"
*
* Adds an entry into the constrain list describing a person, cost center or an application
*/
addConstrain: function(button, event){
console.log('Add_to_constrain clicked');
}
});
Originally this 'selectorcontainer' was put diretly in my app.js. But I extracted it into a stand-alone view. Before the extraction, it works perfect but now it is not working.
BTW, I've two buttons and the first "reset" works fine. So I'm wondering if there's anything wrong with "this.addConstrain" related to scoping.

Answer 1

You're right, it is a scoping issue - this is not the class you're defining; it's the scope at the time the Ext.define function is called (likely window). There are a few ways to handle this. The easiest (in my opinion) is to change your handler to work similarly to your reset handler:
{
text: 'Add to constrain',
handler: function(btn, e) {
//'this' is now the button
this.up('selectorcontainer').addConstrain(btn, e);
}
}
You could also add the buttons as part of the initComponent function instead of defining them as part of the Ext.define config.
initComponent: function() {
//'this' is now the selector container
this.buttons = [{
text: 'Reset',
handler: function(){
console.log("Reset");
this.up('form').getForm().reset();
}
}, {
text: 'Add to constrain',
handler: this.addConstrain
}];
this.callParent();
}

Answer 2

The proper way to design your class is like this. You apply your config settings to the object before you do the callParent.
Ext.define('EDS.view.selector.Container', {
extend: 'Ext.form.Panel',
alias : 'widget.selectorcontainer',
title: 'Selector_V2',
renderTo: 'input-div',
layout: 'fit',
height: '100%',
initComponent: function() {
Ext.applyIf(this, {
items: [
{
xtype: 'tabpanel',
defaults: {
bodyPadding: 10
}
}
],
buttons: [
{
text: 'Reset',
scope: this, // <--- scope to form panel
handler: function(){
console.log("Reset");
this.getForm().reset();
}
},
{
text: 'Add to constrain',
scope : this, // <--- scope to form panel
handler: this.addConstrain
}
]
});
this.callParent(arguments);
}
/*
* Logic for button "Add to constrain"
*
* Adds an entry into the constrain list describing a person, cost center or an application
*/
addConstrain: function(button, event){
console.log('Add_to_constrain clicked');
}
});