Passing Data Between View Controllers in iOS: A Clean Solution Without Breaking MVC

Passing Data Between View Controllers in iOS

In this article, we will explore how to pass data between view controllers in an iOS application without breaking the Model-View-Controller (MVC) pattern. We will consider a scenario where we have a ViewControllerA that loads two additional view controllers (ViewControllerB and ViewControllerC) using a delegate.

Overview of the Problem

We are given a situation where we have a ViewControllerA with a separate UIView attached to it, instead of using a storyboard or xib/nib. The UIView contains a third-party UI component that loads two additional view controllers (ViewControllerB and ViewControllerC) within the ViewControllerA. We want to pass data from ViewControllerA to both ViewControllerB and ViewControllerC.

Approaching the Problem

To solve this problem, we need to rethink our approach. The main issue here is that we are trying to use the view controller as a delegate for creating and passing data to other view controllers, which goes against the MVC pattern.

Step 1: Move the Delegate Method to `ViewControllerA`

We should move the thirdPartyUIComponent(_:) method from the MyViewControllerAView class to the MyViewControllerA class. This is because it’s not appropriate for the view controller to instantiate and handle other view controllers. Instead, the MyViewControllerA will be responsible for creating and managing these additional view controllers.

Step 2: Pass Views Directly to `MyViewControllerAView`

Since we expect that MyViewControllerB and MyViewControllerC need to access their views within the MyViewControllerAView, we should pass these views directly to the MyViewControllerAView. However, instead of passing the view controllers themselves, we will pass only the views (B.view and C.view). This way, the MyViewControllerA can manage its own additional view controllers.

Example Code

Here’s an example of how this could be implemented:

class MyViewControllerA: UIViewController {
    // Create a method to create and return the additional view controllers
    
    func createAdditionalViewControllers() -> (viewB: UIView, viewC: UIView) {
        let viewB = MyViewControllerB()
        let viewC = MyViewControllerC()
        
        // Set up delegates for B and C to receive data from A
        viewB.delegate = self
        viewC.delegate = self
        
        return (viewB.view, viewC.view)
    }
}

class MyViewControllerAView: UIView {
    // Create properties for the views of additional controllers
    
    var viewB: UIView?
    var viewC: UIView?
    
    // Set up the layout for these additional views
}

P.S.: Handling Events with Delegates

If the thirdPartyUIComponent(_:) callback should be called when some UI action is triggered by the user on the MyViewControllerAView, we can use the delegate pattern to pass that event to the MyViewControllerA to handle it cleanly. This will keep our code organized and follow the MVC pattern.

Conclusion

Passing data between view controllers in an iOS application requires careful consideration of the Model-View-Controller (MVC) pattern. By moving the delegate method to the view controller, passing views directly to MyViewControllerAView, and setting up delegates for additional controllers, we can ensure that our code is organized and follows best practices. Remember to use delegates for event handling to keep your code clean and easy to maintain.