Swift 中的多线程

• Thread

• Cocoa Operation （Operation 和 OperationQueue）

  • 面向对象
  • 取消， 依赖， 任务优先级，复杂逻辑，保存业务状态，子类化

• Grand Central Dispath （GCD）

Thread

• 轻量级

• 需要自己管理线程的声明周期和线程同步

快捷方式创建

• detachNewThread(_ block: @escaping() -> void)
  • 输入一个逃逸闭包，可以稍后执行
• detachNewThreadSelector(_ selector: Selector, toTarget target: Any, with argument: Any? )

初始化器

• Thread(target:, selector:, object:)
• 需要手动start线程

for i in 0..<10 {
    Thread.detachNewThread {
        print(i)
    }
}

class ObjectThread {
    func threadTest() {
        let thread = Thread(target: self, selector: #selector(threadWorker), object: nil)
        
        thread.start()
    }
    @objc func threadWorker() {
        print("threadWorker")
    }
}

let obj = ObjectThread()
obj.threadTest()

Operation

• Operation
  • 状态
    • isReady, isExecuting, isFinished, isCancelled
  • sysc
    • main()
  • async
    • start() -> isAsynchronous -> isEexcuting -> isFinished
    • AfNetWorking
  • 添加和移除依赖
• OperationQueue
  • 线程池，可将Opeartion添加到队列中
  • 底层使用GCD
  • maxConcurrentOperationCount 可以设置最大并发数
  • defaultMaxConcurrentOperationCount根据当前系统条件动态确定的最大并发数
  • 可以取消所以Operation，但是目前正在执行的不会取消
  • 所以Operation执行完毕后退出销毁
• BlockOperation

      class ObjectOperation {
          func test()  {
              let operation = BlockOperation { [weak self] in
                  self?.threadWorker()
              }
  
              let queue = OperationQueue()
              queue.addOperation(operation)
          }
  
          @objc func threadWorker() {
              sleep(1)
              print("threadWorker")
          }
      }
  
      let obj = ObjectOperation()
      obj.test()
      print("after invoke test")
  

• 继承Operation

  class ObjectOperation {
      func test()  {
          let operation = MyOperation()
  
          let queue = OperationQueue()
          queue.addOperation(operation)
      }
  
      @objc func threadWorker() {
          sleep(1)
          print("threadWorker")
      }
  }
  
  
  class MyOperation: Operation {
      override func main() {
          sleep(1)
          print("in MyOperation main")
      }
  }
  
  let obj = ObjectOperation()
  obj.test()
  print("after invoke test")
  
  

• Operation 完成的回调
  • completionBlock

  class ObjectOperation {
      func test()  {
          let operation = MyOperation()
          operation.completionBlock = { () -> Void in
              print("completionBlock")
          }
          let queue = OperationQueue()
          queue.addOperation(operation)
      }
  
      @objc func threadWorker() {
          sleep(1)
          print("threadWorker")
      }
  }
  
  
  class MyOperation: Operation {
      override func main() {
          sleep(1)
          print("in MyOperation main")
      }
  }
  
  let obj = ObjectOperation()
  obj.test()
  print("after invoke test")