Architecture

This repo is a suggestion of an architecture to be used in a UIKit MVVM project.

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Rules

- ViewModel does bussiness logics only and is connected to ViewController via a binding Box;

- ViewController is injected with a ViewModel and controls any delegate methods from the View;

- View is used exclusively to create visual stuff;

- View shouldn't have any references to a ViewModel;

- View contains a delegate to connect itself to the ViewController;

(Please check out the example project at the top of the page)

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Box

- A Box is a class that receives a generic type variable as its value. When the value is changed, the box will trigger a closure with this value as the argument;

- This class will be used to connect properties from a ViewModel to a ViewController;

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ViewCode protocol

- This protocol will be used when setting up the layout of a view;

- For example, we can create an extension to a view and subscribe this extension to the ViewCodeProtocol. By doing so, the View will automatically contain a setupUI() method;

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Delegate

- Delegates will be used to connect a ViewController to a View;

- Since a View cannot contain any business logics, it will delegate any non-visual tasks to a ViewController;

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MVVM example

ViewModel

- The ViewModel will be responsible for any business logics, as seen in the method example above (changeText());

- The boxes are created within a ViewModel and are used to keep track of a property's state (just like a @Published property in SwiftUI);

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ViewController

- ViewController has an instance of ViewModel (let viewModel: ViewModel) and sets its value inside the init;

- ViewController also has an instance of View (lazy var myView: View) and sets its delegate inside its closure initializer (myView.delegate = self);

- (Make sure the ViewController conforms to the correct delegate protocol);

- Inside loadView() method, the ViewController's view is set equal to myView. That automatically makes myView fit perfectly inside the ViewController (no need to set any constraints);

- Inside viewDidLoad() method, we create the connection between ViewController and ViewModel by providing an implementation to the closure present inside the ViewModel's box property;

- Inside viewWillAppear() method, we change an information inside myView;

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View

- View has an instance of the ViewController delegate and that's how they are connected to each other;

- View contains two subviews (properties): a label (myLabel) and a button (myButton);

- setupUI() method is called within View's initializer to set subviews layout;

- View contains a method that serves as the target for when myButton is tapped (@objc onTapMyButton());

- When the button is tapped, the View calls its delegate and some logics will be performed by the ViewController. In that case, myLabel's text will be updated;