What's the difference between 'requires' and 'uses' when defining a class?

[dhurlburtusa]

What's the difference between 'requires' and 'uses' when defining a class? I can't find good documentation on this.

What's the advantage of using one over the other?

From a quick glance at the code, it appears the classes declared in the 'uses' array will still be loaded. So why not just put them in the 'requires' array?

[ykey]

From http://dev.sencha.com/deploy/ext-4.0...iew/index.html

Uses are optional class dependencies that are used by, but not required by, a class. These can be loaded asynchronously and do not have to be available for the class to be instantiated.

Not sure that helps any.

[dhurlburtusa]

I must of missed that section in the overview. Thanks.

It helps a little. However, it seems that if a class uses another class, then won't it be required to function correctly?

Maybe it is used when a class may need another class but only if configured in a certain way. For example, class A depends on Class B only if a certain config option is set. Would we have to use Ext.require('ClassB'); if we set this config option or will Class B have already been loaded if it were declared in the 'uses' array?

[Jacky Nguyen]

It's easy to explain with an example:

Ext.define('A', {
    requires: ['B'],
    uses: ['C']
}, function() { // This callback function is invoked right when class A is created
    // Both A and B are ready here, but C is not
});

Break-down of what would happen behind the scene:

- B is dynamically loaded if it doesn't yet exist
- A is created, the callback is executed
- C is loaded

The same applies with:

Ext.require('A', function() {
    // Both A and B are ready here, but C is not 
});

However:

Ext.require('A');

Ext.onReady(function(){
    // A, B and C are all available
});

Another purpose of 'uses' is to 'temporarily' solve deadlock situation. A bad class design would normally lead to a deadlock, for example:

- A extends B
- B mixins C
- C requires A

Sometimes refactoring the code base is not applicable due to certain objective / subjective reasons, and deadlock could be solved by deferring the loading priority of a certain class. The above example could be changed to:

- A extends B
- B mixins C
- C uses A

This occasionally happened when migrating dinosaur code to the new class system.

[steffenk]

so the conclusion sounds like: don't use "uses" regulary, it's just needed for some tenuous situations. Right?

[ykey]

Please add this explanation to the docs.

[BrightSoul]

Is this available in Sencha Touch as well? I can't find Ext.define and Ext.require in Sencha Touch Api Documentation...

If not, is it ok to use Ext Core alongside Sencha Touch?