Strategy Selector

StrategySelector.swift

class StrategySelector {
    
    private var strategy: (() -> Void)!
    private var state: String = ""

    init() {
        strategy = strategyA
    }
    
    func execute() {
        strategy()
    }
    
    func read() -> String {
        state
    }
    
    func selectStrategyA() {
        strategy = strategyA
    }
    
    func selectStrategyB() {
        strategy = strategyB
    }
    
    private func strategyA() {
        state.append("A")
    }
    
    private func strategyB() {
        state.append("B")
    }
}

let selector = StrategySelector()
selector.execute()
selector.selectStrategyB()
selector.execute()
selector.selectStrategyA()
selector.execute()
selector.execute()
selector.read() // ABAA