DispatchGroup在所有休假电话前通知

Question

我有一个iOS应用程序，它运行多个类(每个类在一个单独的线程中)，我想在所有类完成运行时收到通知。

所以我有一个基类：

class BaseClass {
var completeState: CompleteState

init(completeState: CompleteState) {
self.completeState = completeState
self.completeState.dispatch.enter()
}

func start() { }
}

这就是完整状态类：

class CompleteState {
let userId:String
let dispatch = DispatchGroup()

init(userId:String) {
self.userId = userId
dispatch.notify(queue: DispatchQueue.main) {
print("Finish load all data")
}
}
}

我有多个从BaseClass继承的类，它们都是这样的形式：

class ExampleClass1: BaseClass {
override func start() {
DispatchQueue.global().async {
print("ExampleClass1 - Start running")
//DOING SOME CALCULATIONS

print("ExampleClass1 - Finish running")
self.completeState.dispatch.leave()
}
}
}

这是运行所有这些的代码：

public class RunAll {
let completeState: CompleteState
let classArray: [BaseClass]

public init(userId: String) {
self.completeState = CompleteState(userId: userId)
classArray = [ExampleClass1(completeState: completeState),
ExampleClass2(completeState: completeState),
ExampleClass3(completeState: completeState),
ExampleClass4(completeState: completeState),
ExampleClass5(completeState: completeState),
ExampleClass6(completeState: completeState),
ExampleClass7(completeState: completeState),
ExampleClass8(completeState: completeState),
ExampleClass9(completeState: completeState)]
startClasses()
}

private func startClasses() {
for foo in classArray {
foo.start()
}
}
}

问题是，在所有类完成工作之前，我会调用dispatch.notify，你知道问题出在哪里吗？

Answer 1

notify的文档说明：

当与调度组关联的所有块都已完成时，此函数会调度要提交到指定队列的通知块。如果组为空(没有块对象与调度组关联)，则会立即提交通知块对象。提交通知块时，组为空。

您正在CompleteStateinit中调用dispatch.notify()。在调用notify时，调度组是空的，因为您还没有创建一个名为start的BaseClass子类，也就是输入调度组的地方。

因为当调度组为空时调用notify，所以块会立即提交。

研究OperationQueue可能是值得的，但如果你想使用你所拥有的，你可以将notify从init:中分离出来

lass CompleteState {
let userId:String
let dispatch = DispatchGroup()

init(userId:String) {
self.userId = userId
}

func registerCompletionBlock(handler: @escaping () -> Void) {
self.dispatch.notify(queue: DispatchQueue.main, execute: handler)
}
}

然后，您将在调用startClasses后提供完成块

public init(userId: String) {
self.completeState = CompleteState(userId: userId)
classArray = [ExampleClass1(completeState: completeState),
ExampleClass2(completeState: completeState),
ExampleClass3(completeState: completeState),
ExampleClass4(completeState: completeState),
ExampleClass5(completeState: completeState),
ExampleClass6(completeState: completeState),
ExampleClass7(completeState: completeState),
ExampleClass8(completeState: completeState),
ExampleClass9(completeState: completeState)]
startClasses()
self.completeState.registerCompletionBlockHandler {
print("Finish load all data")
}
}