swift - The command pattern
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The command pattern provides a mechanism by which details of how to invoke a method can beencapsulated so that the method can be invoked later or by a different component.
client:
let calc = Calculator(); calc.add(10); calc.multiply(4); calc.subtract(2); println("Calc 1 Total: (calc.total)"); let macro = calc.getMacroCommand(); let calc2 = Calculator(); macro(calc2); println("Calc 2 Total: (calc2.total)");
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pattern:
//1
import Foundation; class Calculator { private(set) var total = 0; typealias CommandClosure = (Calculator -> Void); private var history = [CommandClosure](); private var queue = dispatch_queue_create("arrayQ",DISPATCH_QUEUE_SERIAL);
func add(amount:Int) { addMacro(Calculator.add,amount: amount); total += amount; }
func subtract(amount:Int) { addMacro(Calculator.subtract,amount: amount); total -= amount; }
func multiply(amount:Int) { addMacro(Calculator.multiply,amount: amount); total = total * amount; }
func divide(amount:Int) { addMacro(Calculator.divide,amount: amount); total = total / amount; }
private func addMacro(method:Calculator -> Int -> Void,amount:Int) { dispatch_sync(self.queue,{() in self.history.append({ calc in method(calc)(amount)}); }); }
func getMacroCommand() -> (Calculator -> Void) { var commands = [CommandClosure](); dispatch_sync(queue,{() in commands = self.history }); return { calc in if (commands.count > 0) { for index in 0 ..< commands.count { commands[index](calc); } } }; } }
//2
protocol Command { func execute(receiver:Any); } class CommandWrapper : Command { private let commands:[Command];
init(commands:[Command]) { self.commands = commands; }
func execute(receiver:Any) { for command in commands { command.execute(receiver); } } } class GenericCommand<T> : Command { private var instructions: T -> Void;
init(instructions: T -> Void) { self.instructions = instructions; }
func execute(receiver:Any) { if let safeReceiver = receiver as? T { instructions(safeReceiver); } else { fatalError("Receiver is not expected type"); } }
class func createCommand(instuctions: T -> Void) -> Command { return GenericCommand(instructions: instuctions); } } （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |