在Swift / Objective-C中实现下一个线程解决方案 [英] Implementing next threading solutions in Swift / Objective-C

问题描述

我开始学习 iOS 的编程，我想了解如何在 Swift中使用线程实现下一个 Java 函数，以及 Objective-C （在我的应用中，我也有一些使用此语言的代码）

I started to learn programming for iOS and I want to find out how to implement next Java functions with threads in Swift, and also in Objective-C (in my app I have some code using this language too)

Java线程（用于Android应用程序）

1）等待两个或多个线程完成

1) Wait for two or more threads to finished

final CountDownLatch latch = new CountDownLatch(2);

// start thread #1
new Thread(new Runnable() {
    @Override
    public void run() {
        // do some work
        latch.countDown();
    }
}).start();

// start thread #2
new Thread(new Runnable() {
    @Override
    public void run() {
        // do some work
        latch.countDown();
    }
}).start();

// wait for 2 threads to end (finish)
try {
    latch.await();
} catch (InterruptedException e) {
    //
}
// two threads are finished 
// do other work

2）仅当前一个线程此时完成或任何线程尚未启动时才启动新线程（ mThread == null ）

2) Start new thread only if previous one was finished at this time or any thread wasn't started yet (mThread == null)

private Thread mThread = null; // class field

。

// check if thread has completed execution
if ((mThread != null && mThread.getState() == Thread.State.TERMINATED)
    || mThread == null) {

    mThread = new Thread(new Runnable() {
        @Override
        public void run() {
            // do some work
        }
    });
    mThread.start();
}

推荐答案

我对第一个的回答（ 1）解决方案（等待所有线程完成执行）：

my answer for the first (1) solution (wait until all threads finish its execution):

dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
    // block1
    NSLog(@"Task Block1");
    [NSThread sleepForTimeInterval:6.0];
    NSLog(@"Task Block1 End");
});


dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
    // block2
    NSLog(@"Task Block2");
    [NSThread sleepForTimeInterval:5.0];
    NSLog(@"Task Block2 End");
});


dispatch_group_wait(group, DISPATCH_TIME_FOREVER); // blocks current thread

第二个解决方案（2）

我没有找到像 isRunning 这样的GCD方法，所以我只使用布尔变量

I didn't find for GCD method like isRunning, so I just use Boolean variable

在启动异步任务集变量isRunning为true之前
...
...
当异步任务完成时我们可以使用下一个回调：

before starting async task set variable isRunning to true ... ... when async task is finished we can use next callback:

dispatch_group_notify(_signInitThread, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^ {
    isRunning = false;
});

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