StrategyExample

SwiftStrategy.swift

import Foundation

// First define the algorithm protocol.
protocol LoadBehaviour {
    func execute() -> String
}

// Define the algorithms.
// Algorithm 1
class CoreDataManager: LoadBehaviour {
    func execute() -> String {
        return "CoreData should be called.."
    }
}

// Algorithm 2
class ApiManager: LoadBehaviour {
    func execute() -> String {
        return "API is safe to call, there's internet."
    }
}

// The client calling LoadBehaviour.
class LoadClient: AnyObject {
    // Behaviour can be changed during runtime.
    var behaviour: LoadBehaviour
    
    // Make sure the client has a default behaviour.
    init(_ initialBehaviour: LoadBehaviour) {
        self.behaviour = initialBehaviour
    }
    
    func load() {
        print(self.behaviour.execute())
    }
}

// Create the client with a default behaviour.
// We don't know whether we have internet, so first
// load data from CoreData, just to be sure.
var client = LoadClient(CoreDataManager())
client.load()

// Imagine we suddenly connect to WiFi.
client.behaviour = ApiManager()

// A few minutes later we want new data, but now we have a internet connection.
client.load()