Question

我遇到的问题是为什么以下代码打印出来的优先级是一样的？为什么是这样？非常感谢你。

    print("main:\(Thread.current)")
    print("thread main priorities:\(Thread.current.threadPriority)")

    DispatchQueue.global(qos: .utility).async {
        print("utility:\(Thread.current)")
        print("thread utility priorities:\(Thread.current.threadPriority)")
    }

    DispatchQueue.global(qos: .background).async {
        print("background:\(Thread.current)")
        print("thread background priorities:\(Thread.current.threadPriority)")
    }

    DispatchQueue.global(qos: .userInteractive).async {
        print("userInteractive:\(Thread.current)")
        print("thread userInteractive priorities:\(Thread.current.threadPriority)")
    }

    DispatchQueue.global(qos: .userInitiated).async {
        print("userInitiated:\(Thread.current)")
        print("thread userInitiated priorities:\(Thread.current.threadPriority)")
    }

日志：

main：{number = 1，name = main} 主要优先事项：0.5

userInteractive：{number = 3，name =（null）}

实用程序：{number = 5，name =（null）}

background：{number = 6，name =（null）}

thread userInteractive priority：0.5

userInitiated：{number = 4，name =（null）}

线程实用程序优先级：0.5

线程后台优先级：0.5

线程userInitiated priority：0.5

Answer 1

正如您在文档中看到的那样：

@available(iOS 4.0, *)
open var threadPriority: Double // To be deprecated; use qualityOfService below

不推荐使用threadPriority。此外，Apple的GCD团队对Thread-Queue主题非常清楚。 GCD将为您管理线程。队列优先级不是线程优先级。看一下这个例子，这是你在这里发布的代码，我刚刚添加了＆＃34; qos_class_self（）。rawValue＆＃34;，这实际上是你应该如何测试QoS，而不是＆＃34; threadPriority＆＃34;

print("main:\(Thread.current), Thread main priorities:\(Thread.current.threadPriority), QoS: \(qos_class_self().rawValue)")

DispatchQueue.global(qos: .utility).async {
    print("utility:\(Thread.current), Thread utility priorities:\(Thread.current.threadPriority), QoS: \(qos_class_self().rawValue)")
}

DispatchQueue.global(qos: .background).async {
    print("background:\(Thread.current), Thread background priorities:\(Thread.current.threadPriority), QoS: \(qos_class_self().rawValue)")
}

DispatchQueue.global(qos: .userInteractive).async {
    print("userInteractive:\(Thread.current), Thread userInteractive priorities:\(Thread.current.threadPriority), QoS: \(qos_class_self().rawValue)")
}

DispatchQueue.global(qos: .userInitiated).async {
    print("userInitiated:\(Thread.current), Thread userInitiated priorities:\(Thread.current.threadPriority), QoS: \(qos_class_self().rawValue)")
}

我还合并了每个封闭的打印件，因此它们不会在日志中的不同行中被打乱。这表明维护了QoS，而不推荐使用threadPriority。

main:<NSThread: 0x6100000762c0>{number = 1, name = main}, Thread main priorities:0.5, QoS: 33
userInteractive:<NSThread: 0x610000261fc0>{number = 4, name = (null)}, Thread userInteractive priorities:0.5, QoS: 33
utility:<NSThread: 0x618000079100>{number = 3, name = (null)}, Thread utility priorities:0.5, QoS: 17
userInitiated:<NSThread: 0x608000078380>{number = 5, name = (null)}, Thread userInitiated priorities:0.5, QoS: 25
background:<NSThread: 0x610000262000>{number = 6, name = (null)}, Thread background priorities:0.5, QoS: 9

所以，最后，带走的不是思考线程，而是考虑队列，QoS和知道GCD将为您管理线程。与队列出现GCD之前我们习惯的概念截然不同。

iOS GCD全局队列优先级均为0.5

1 个答案: