How do I apply the delegate, observer, and singleton patterns appropriately?

This article explains how to appropriately implement the delegate, observer, and singleton design patterns in Swift. These design patterns help to create a structured and clean codebase, enhancing code reusability and maintainability.

Delegate Pattern

The delegate pattern allows one object to communicate with another without requiring tight coupling. It is commonly used in iOS for components like UITableView. Here’s a simple example:


        class DataLoader {
            var delegate: DataLoaderDelegate?
            
            func loadData() {
                // Simulate data loading
                let data = "Data Loaded"
                delegate?.didLoadData(data: data)
            }
        }
        
        protocol DataLoaderDelegate {
            func didLoadData(data: String)
        }

        class ViewController: DataLoaderDelegate {
            let dataLoader = DataLoader()
            
            func setup() {
                dataLoader.delegate = self
                dataLoader.loadData()
            }
            
            func didLoadData(data: String) {
                print(data)
            }
        }

Observer Pattern

The observer pattern is used when an object needs to notify other objects about changes in its state. This is useful in situations like notifications or event handling. Here’s a basic example:


        class Notifier {
            private var observers = [Observer]()
            
            func addObserver(_ observer: Observer) {
                observers.append(observer)
            }
            
            func notifyObservers() {
                for observer in observers {
                    observer.update()
                }
            }
        }

        protocol Observer {
            func update()
        }

        class Listener: Observer {
            func update() {
                print("Observer notified!")
            }
        }

Singleton Pattern

The singleton pattern restricts a class to a single instance and provides a global point of access to it. This is often used for managing shared resources like configuration settings or a shared database connection.


        class Singleton {
            static let shared = Singleton()
            
            private init() {
                // Private initialization to prevent others from using the default '()' initializer
            }
            
            func doSomething() {
                print("Doing something...")
            }
        }
        
        // Usage
        Singleton.shared.doSomething()

How do I apply the delegate, observer, and singleton patterns appropriately?

Delegate Pattern

Observer Pattern

Singleton Pattern

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How do I apply the delegate, observer, and singleton patterns appropriately?

Delegate Pattern

Observer Pattern

Singleton Pattern

Related Questions

Popular Topics

Recent Languages