Difference between update and apply magic methods

[wprater]

I've seen them both used in the source, but the docs state the new class system uses the applyConfigName magic method and does not mention the updateConfigName method. These seem to be generated with the #initConfig method.

Insights are appreciated!

[mitchellsimoens]

The properties in the config Object automatically create the getter and setter functions for those properties. For instance, say I have a Button like this:

Ext.define('My.Button', {
    extend : 'Ext.Button',
    xtype  : 'mybutton',

    config : {
        action : 'delete'
    }
});

It will create the getAction and setAction methods. All the getAction does is return the action property on the button, simple. The setAction also sets the action property but quite a lot of times you need to do other things other than just setting the property, this is where the apply and update methods are used.

So you created an instance of the button but want to change the action using the setAction like this:

button.setAction('SAVE');

This is what happens... you execute the setAction, it will first check to see if there is the applyAction method and if so it will execute it passing in the value you past setAction. In this method, you can do different things to transform the value like maybe we want to make sure the text is always lower case. In the apply action, you need to return the transformed value:

applyAction: function(action) {
    return action.toLowerCase();
}

After the apply method has been fired and it returned the transformed value, the property is then set on the button. But what if we need to take action after the property has been set? This is where the update method comes in. I normally use this for updating DOM elements but you can do whatever the need requires you to do. Let's change the ui of the button based on action:

updateAction: function(action) {
    var ui;

    if (action === 'save') {
        ui = 'confirm';
    } else if (action === 'delete') {
        ui = 'decline';
    }

    this.setUi(ui);
}

Pretty much the workflow of the setter method. To finalize the button code all in one this is what it would look like:

Ext.define('My.Button', {
    extend : 'Ext.Button',
    xtype  : 'mybutton',

    config : {
        action : 'delete'
    },

    applyAction: function(action) {
        return action.toLowerCase();
    },

    updateAction: function(action) {
        var ui;

        if (action === 'save') {
            ui = 'confirm';
        } else if (action === 'delete') {
            ui = 'decline';
        }

        this.setUi(ui);
    }
});

[wprater]

Great response! I could not find the class creator in the source folder for ST2. The code appears to be in the concatenated source, but not the individual source files.

[mitchellsimoens]

Check out the EventedBase.js file, the Class.addMember about half way down is where this happens.

[vitalyx]

Is the updateProperty() method being invoked each time we set a property via setProperty() or there is some extra logic to it?

I'm trying to use setGrouper() on a store, but only applyGrouper is called as a result, but not the updateGrouper(). Why this behavior? I'm pretty sure the new grouper is different from the old one.

[mitchellsimoens]

The updater will get called as long as the value is not undefined. So if you execute the setter with a valid value, it hits the applier but not the updater that would tell me the applier is not returning a value.

[vitalyx]

In this case the applier is the standard method of the Ext.data.Store

applyGrouper: function(grouper) {
        if (typeof grouper == 'string') {
            grouper = {
                property: grouper
            };
        }
        else if (typeof grouper == 'function') {
            grouper = {
                groupFn: grouper
            };
        }


        grouper = Ext.factory(grouper, Ext.util.Grouper, this.getGrouper());
        return grouper;
    }

and it does return a value.
Also, the setter is given a perfectly valid value, which is an object.


I actually already found the reason for this error and submitted a bug report:


http://www.sencha.com/forum/showthre...oldValue-check

[minamu1]

I had spent quite some time reading about this in the Class System docs, list object docs, the complicated datamap setup and the cryptic apply/update code with little understanding, until I finally found this. The selected "Best Answer" should be in the Sencha docs, added to the "The Class System" topic for ST (would probably apply to ExtJS as well).