Controllers

Controllers are responsible for responding to events that occur within your app. If your app contains a Logout button that your user can tap on, a Controller listens to the Button's tap event and takes the appropriate action. While View classes handles the display of data and Model classes handle the loading and saving of data, Controller classes are the glue that binds Views and Models together.

Relation to Ext.app.Application

Controllers exist within the context of an Application. An Application usually consists of a number of Controllers, each of which handle a specific part of the app. For example, an Application that handles the orders for an online shopping site might have controllers for Orders, Customers, and Products.

All Controllers used by an Application are specified in the Application's controllers config. The Application automatically instantiates each Controller and keeps references to each of them, so in most cases you do not need to instantiate Controllers directly. By convention each Controller is named after the entity (usually the Model) that it manages, usually in the plural - for example, if your app is called 'MyApp' and you have a Controller that manages Products, the convention is to create a MyApp.controller.Products class in the file app/controller/Products.js.

Launching

There are four main phases in your Application's launch process, two of which pertain to a Controller. First, each Controller is able to define an init function, which is called before the Application launch function. Second, after the Application and Profile launch functions have been called, as the last phase of the process the Controller's launch function is called, as follows:

1. Controller#init functions called
2. Profile#launch function called
3. Application#launch function called
4. Controller#launch functions called

Most of the time your Controller-specific launch logic should go into your Controller's launch function. Because the controller's launch function is called after the Application and Profile launch functions, your app's initial UI is expected to be in place at this point. If you need to do some Controller-specific processing before app launch, you can implement a Controller init function.

Refs and Control

The centerpiece of Controllers are the twin configurations refs and control. These are used to gain references to Components inside your app and to take action on them, based on the events that they fire. In the following sections we first look at the refs config.

Refs

Refs leverage the powerful ComponentQuery syntax to easily locate Components on your page. For each Controller we can define as many refs as required, for example in the following example we define a ref called 'nav' that finds on the page a Component with the 'mainNav' ID. We then use that refs in the subsequent addLogoutButton function, as shown in this sample:

Ext.define('MyApp.controller.Main', {
    extend: 'Ext.app.Controller',

    config: {
        refs: {
            nav: '#mainNav'
        }
    },

    addLogoutButton: function() {
        this.getNav().add({
            text: 'Logout'
        });
    }
});

Usually, a ref is just a key/value pair - the key ('nav' in this case) is the name of the reference that is to be generated, while the value ('#mainNav' in this case) is the ComponentQuery selector used to find the Component.

We have then created the addLogoutButton function which uses this ref via its generated 'getNav' function. This getter function is automatically generated based on the refs you define and always follows the same format - 'get', followed by the capitalized ref name. In this case we are treating the nav reference as a Toolbar, and we add a Logout button to it when our function is called. This ref would recognize a Toolbar such as the following:

Ext.create('Ext.Toolbar', {
    id: 'mainNav',

    items: [
        {
            text: 'Some Button'
        }
    ]
});

Assuming that this Toolbar has already been created by the time we run the 'addLogoutButton' function (we will see later how that is invoked), it will get the second button added to it.

Advanced Refs

Refs can also be passed additional options, beyond name and selector. These options are autoCreate and xtype, which are almost always used together:

Ext.define('MyApp.controller.Main', {
    extend: 'Ext.app.Controller',

    config: {
        refs: {
            nav: '#mainNav',

            infoPanel: {
                selector: 'tabpanel panel[name=fish] infopanel',
                xtype: 'infopanel',
                autoCreate: true
            }
        }
    }
});

We have added a second ref to our Controller. Again the name is the key, 'infoPanel' in this case, but this time we have passed an object as the value. This time we have used a more complex selector query - imagine that your app contains a tab panel and that one of the items in the tab panel is named 'fish'. The previously specified selector matches any Component with the 'infopanel' xtype inside the tab panel item.

The difference here is that, if infopanel does not exist already inside the 'fish' panel, it will be automatically created when you run this.getInfoPanel inside your Controller. The Controller is able to create the infopanel Component because we provided the xtype for instantiating it, in case the selector did not return anything.

Control

The related config to refs is control. Control is the means by which your Controller listens to events fired by app Components and reacts in some way. The Control config accepts both ComponentQuery selectors and refs as its keys, and listener objects as values, as shown in the following example:

Ext.define('MyApp.controller.Main', {
    extend: 'Ext.app.Controller',

    config: {
        control: {
            loginButton: {
                tap: 'doLogin'
            },
            'button[action=logout]': {
                tap: 'doLogout'
            }
        },

        refs: {
            loginButton: 'button[action=login]'
        }
    },

    doLogin: function() {
        // called whenever the Login button is tapped
    },

    doLogout: function() {
        // called whenever any Button with action=logout is tapped
    }
});

In the previous example we have set up two control declarations - one for the loginButton ref and the other for any Button that has been given the 'logout' action. For each declaration we passed in a single event handler - in each case listening for the 'tap' event - and specified the action that should be called when that Button fires the tap event. Note that we specified both the 'doLogin' and 'doLogout' methods as strings inside the control block - this is important.

In each control declaration, you can listen to as many events as you like, and mix and match ComponentQuery selectors and refs as the keys.

Routes

As of Sencha Touch, Controllers can directly specify which routes they are interested in. This enables us to provide history support within our app, as well as the ability to deeply link to any part of the application that we provide a route for.

For example, let us assume that we have a Controller responsible for logging in and viewing user profiles, and want to make those screens accessible via urls. We could achieve that as follows:

Ext.define('MyApp.controller.Users', {
    extend: 'Ext.app.Controller',

    config: {
        routes: {
            'login': 'showLogin',
            'user/:id': 'showUserById'
        },

        refs: {
            main: '#mainTabPanel'
        }
    },

    // uses our 'main' ref above to add a loginpanel to our main TabPanel (note that
    // 'loginpanel' is a custom xtype created for this application)
    showLogin: function() {
        this.getMain().add({
            xtype: 'loginpanel'
        });
    },

    // Loads the User then adds a 'userprofile' view to the main TabPanel
    showUserById: function(id) {
        MyApp.model.User.load(id, {
            scope: this,
            success: function(user) {
                this.getMain().add({
                    xtype: 'userprofile',
                    user: user
                });
            }
        });
    }
});

The routes specified previously map the contents of the browser address bar to a Controller function that is called when the route is matched. The routes can be simple text like the login route, which matches against http://myapp.com/#login, or may contain wildcards such as the 'user/:id' route, which matches urls like http://myapp.com/#user/123. Whenever the address changes, the Controller automatically calls the specified function.

Note that the showUserById function first has to load the User instance. Whenever you use a route, the function that is called by that route is completely responsible for loading its data and restoring the state. This is because a user could either send that url to another person or could simply refresh the page, which wipes any cached data that you had already loaded. In the application architecture guides you can find a more thorough discussion on restoring state with routes.

Before Filters

An additional functionality that Controllers provide within the context of Routing is the ability to define filter functions that are run before the function specified in the route. These are an excellent place to authenticate or authorize users for specific actions, or to load classes that are not yet on the page. For example, let us say we want to authenticate a user before allowing him to edit a Product in an e-commerce backend application:

Ext.define('MyApp.controller.Products', {
    config: {
        before: {
            editProduct: 'authenticate'
        },

        routes: {
            'product/edit/:id': 'editProduct'
        }
    },

    // this is not directly because our before filter is called first
    editProduct: function() {
        //... performs the product editing logic
    },

    // this is run before editProduct
    authenticate: function(action) {
        MyApp.authenticate({
            success: function() {
                action.resume();
            },
            failure: function() {
                Ext.Msg.alert('Not Logged In', "You can't do that, you're not logged in");
            }
        });
    }
});

Whenever the user navigates to an URL such as http://myapp.com/#product/edit/123, the Controller's authenticate function is called and is passed the Ext.app.Action that would have been executed if the before filter did not exist. An Action simply represents the Controller function (editProduct in this case) and other data, such as the ID parsed from the url.

The filter can perform any kind of processing it needs to, either synchronously or asynchronously. In this case we are using our application's authenticate function to verify that the user is currently logged in. Since this could entail an AJAX request to check the user's credentials on the server, it runs asynchronously - if the authentication was successful, we continue the action by calling action.resume(), if not we tell the user that he needs to log in first.

Before filters can also be used to load additional classes before certain actions are performed. For example, if some actions are rarely used, you may wish to defer loading of their source code until they are needed, so that the application boots up faster. To achieve this you can simply set up a filter that uses Ext.Loader to load code on demand.

Any number of before filters can be specified for each action, to use more than one filter simply pass in an array:

Ext.define('MyApp.controller.Products', {
    config: {
        before: {
            editProduct: ['authenticate', 'ensureLoaded']
        },

        routes: {
            'product/edit/:id': 'editProduct'
        }
    },

    // this is not directly because our before filter is called first
    editProduct: function() {
        //... performs the product editing logic
    },

    // this is the first filter that is called
    authenticate: function(action) {
        MyApp.authenticate({
            success: function() {
                action.resume();
            },
            failure: function() {
                Ext.Msg.alert('Not Logged In', "You can't do that, you're not logged in");
            }
        });
    },

    // this is the second filter that is called
    ensureLoaded: function(action) {
        Ext.require(['MyApp.custom.Class', 'MyApp.another.Class'], function() {
            action.resume();
        });
    }
});

The filters are called in order, and each must call action.resume() to continue the processing.

Profile-Specific Controllers

Superclass, shared stuff:

Ext.define('MyApp.controller.Users', {
    extend: 'Ext.app.Controller',

    config: {
        routes: {
            'login': 'showLogin'
        },

        refs: {
            loginPanel: {
                selector: 'loginpanel',
                xtype: 'loginpanel',
                autoCreate: true
            }
        },

        control: {
            'logoutbutton': {
                tap: 'logout'
            }
        }
    },

    logout: function() {
        // code to close the user's session
    }
});

Phone Controller:

Ext.define('MyApp.controller.phone.Users', {
    extend: 'MypApp.controller.Users',

    config: {
        refs: {
            nav: '#mainNav'
        }
    },

    showLogin: function() {
        this.getNav().setActiveItem(this.getLoginPanel());
    }
});

Tablet Controller:

Ext.define('MyApp.controller.tablet.Users', {
    extend: 'MyApp.controller.Users',

    showLogin: function() {
        this.getLoginPanel().show();
    }
});