CODEWITHSUNDEEP
javascriptextjs
Alex
Alex

Reputation: 2976

Extjs 6: what does 'onClassExtended' do when defining a class?

Ext.define('Algo.data.Simulated', {
    requires: [
        //....
    ],

    onClassExtended: function (cls, data) {
        // ....
    }
})

Here is the code. I cannot find any documentation about it on Sencha's website. Also, what do cls and data mean?

Upvotes: 0

Views: 215

Answers (1)

Alexander
Alexander

Reputation: 20224

Well, the easy way to find out would be to define a new class, override onClassExtended, and use two console.log to log the values.

But let's take the hard way, searching the ExtJS codebase for onClassExtended. Notepad++ does provide a search that can find a string in all files in a directory, that's really useful with ExtJS.

You will find that the property is first processed in packages\core\src\class\Class.js, l. 347 ff., and that the processing does nothing but add the function to $onExtended. So we search for $onExtended, finding that usually, $onExtended is called in triggerExtended(), which is called from, you guess it, packages\core\src\class\Class.js, l. 347 ff. (but it is called BEFORE the current class's onClassExtended is added to the list!)

Class.triggerExtended.apply(Class, arguments);

together with 

function(Class, data, hooks) {

means that cls will contain whatever is in Class, and data will contain whatever data has been put into the extend method.

Looking at the code, I believe that these two parameters are the two parameters of Ext.define:

Ext.define(
   'MyApp.data.Test', // <- Class
    { // data object
       extend:'Ext.class.Base' // <- "data.extend" is deleted in line 357
       ...
    }
);

It seems onClassExtended does allow you to define, in EVERY class in a hierarchy, a processing directive that can transform the class definition. They are executed, beginning with the topmost (the most special class) and ripple through until they reach the base class, Ext.class.Base.

Unlike the constructor, these transformations are executed during definition of a child class, not during instance creation.

Upvotes: 3

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