ios - OperationQueue 执行时未调用操作子类 "main"方法？

Question

我创建了一个继承自基类“Operation”的子类“MyOperation”。我在“MyOperation”中添加了一个函数，该函数在类实例化时被调用。但是，当创建操作类并将其添加到操作队列时，不会调用“main”方法。

class MyOperation: Operation {

let iterations:Int
let tag:String

init(iterations:Int, tag:String) {
    self.iterations = iterations
    self.tag = tag
}

/**
 When Operation queue begins execution it calls the main method without parameters, so any parameters needed should be passed through initializer.
 **/

override func main() {
    performCalculation()
}

func performCalculation(){
    let start = CFAbsoluteTimeGetCurrent()
    for _ in 0..<iterations {

        self.doCalculations()
    }
    let end = CFAbsoluteTimeGetCurrent()
    print("time for \(tag):\(end-start)")
}

func doCalculations() {

    let x = 100
    let y = x*x
    let _ = y/x
}

}

我正在从 View Controller 的 ViewDidLoad 调用 MyOperation 类。

override func viewDidLoad() {
    super.viewDidLoad()
   createOperationQueuewithMyOperationClass()
}

func createOperationQueuewithMyOperationClass(){


    let operationQueue = OperationQueue()
    operationQueue.addOperation {
        MyOperation(iterations: 10000000, tag: "Operation-1")
    }

    operationQueue.addOperation {
      MyOperation(iterations: 1000, tag: "Operation-2")
    }

    operationQueue.addOperation {
      MyOperation(iterations: 100000, tag: "Operation-3")
    }
}

Answer 1

您使用了错误的 addOperation。您所拥有的只是将一个 block 操作添加到队列中，而该 block 正在创建该操作并且不对其进行任何操作。你想要这个:

operationQueue.addOperation(MyOperation(iterations: 100000, tag: "Operation-3"))

请注意缺少大括号 { ... } 和圆括号。

您正在调用 addOperation(() -> Void)而不是 addOperation(Operation)