Question

I use the iOS UI Automation framework to make sure my iPhone app rocks.

Everybody who uses this framework would tell you that it’s great, but that it’s lacking a lot of structure.

So I have to deal with instances of UIAWindow, which represent different screens of my app. To be more object-oriented, I’d like to have a specific class for each screen, so I could add specific methods, like

myScreen1.tapDoneButton();
var total = myScreen2.getNumberOfElements();

For the moment, I’m able to achieve this by passing the instances of UIAWindow to functions that will add the appropriate methods, like this :

function makeMainScreen(actualScreen)
{   
    actualScreen.constructor.prototype.getAddButton = function() {
        return this.buttons()["add button"];
    };
    actualScreen.constructor.prototype.tapAddButton = function() {
        this.getAddButton().tap();
    };
    // Add any desired method...

return actualScreen;
}

It works fine, I use it like this :

var mainScreen = makeMainScreen(app.mainWindow());
mainScreen.tapAddButton();

But that doesn’t seem object-oriented enough, I would like to create real objects, using the new and this keywords, so I’d have a declaration like this :

function MainScreen(actualScreen){
  // This line doesn't work : because 'this' is immutable
  this = actualScreen;

  this.tapAddButton = function(){
    this.getAddButton().tap();
  }

  //...

}

And I’d use it like this :

var mainScreen = new MainScreen(app.mainWindow());
mainScreen.tapAddButton();

I thought I could save the actualScreen as a property of the object (Like in Grace Shao’s answer below), and call all the methods on it, but I’d like keep the original UIAWindow methods.

Does anybody know how to do this?
Or perhaps what I’m trying to achieve doesn’t make sense, in which case I’d be happy to know.

Answer 1

If I understand correctly, you could try the following:

function MainScreen(actualScreen){
    this.screen = actualScreen;
}

MainScreen.prototype.tapAddButton = function () {
    this.screen.getAddButton().tap();
};

MainScreen.prototype.getScreen = function () {
    return this.screen;
};

//...

var mainScreen = new MainScreen(app.mainWindow());

mainScreen.tapAddButton();

You are correct that you cannot assign anything to this. You could also define the methods inside the constructor MainScreen, but they would be considered privileged members.

function MainScreen(actualScreen){
    this.screen = actualScreen;

    this.tapAddButton = function () {
        this.screen.getAddButton().tap();
    };
}

If you dont want them to be privileged members, it is better to define them outside the constructor. Otherwise, the members will be initialized over and over again everytime when you instantiate a new object.

Updated:
You could also wrappers for the methods of screen inside the constructor as below.

var prop;

for (prop in actualScreen) {
    if (typeof actualScreen[prop] !== 'Function') {
        continue;
    }
    this[prop] = function () {
        return actualScreen[prop].apply(actualScreen, arguments);
    };
}