swift3.0开发中的GCD

队列

DispatchQueue 可以执行串行，并发。FIFO

创建队列， label 唯一的标识，建议用DNS命名

let queue = DispatchQueue(label: "com.nip.queue")

同步执行： sync

func gcd_test1() {
    // 创建一个队列，并给队列提供一个独一无二的标签，DNS
    let queue = DispatchQueue(label: "com.newsinpalm")
    
    // 队列创建完，就可以执行同步sync，异步操作async
    queue.sync {
        for i in 0 ..< 10 {
            // 先打印完
            print("🔴",i)
        }
    }
    for i in 100 ..< 110 {
        // 再打印
        print("😷",i)
    }
}

异步执行：async

let queue = DispatchQueue(label: "com.newsinpalm")

// 队列创建完，就可以执行同步sync，异步操作async
queue.async {
    for i in 0 ..< 10 {
        print("🔴",i)
    }
}
queue.async {
    for i in 100 ..< 110 {
        print("😷",i)
    }
}

队列的优先级

枚举类型DispatchQoS

public enum QoSClass {

        case background

        case utility

        case `default`

        case userInitiated

        case userInteractive

        case unspecified

        public init?(rawValue: qos_class_t)

        public var rawValue: qos_class_t { get }
    }

优先级顺序

userInteractive
userInitiated
default
utility
background
unspecified

代码：

let queue1 = DispatchQueue(label: "com.nip.queue1", qos: DispatchQoS.default)
let queue2 = DispatchQueue(label: "com.nip.queue2", qos: DispatchQoS.userInteractive)
queue1.async {
    for i in 0 ..< 10 {
        print("👨‍❤️‍👨",i)
    }
}

queue2.async {
    for i in 100..<110{
        print("👃🏻",i)
    }
}

异步并发，自动执行

// 异步并发队列，自动执行
    func gcd_test3() {
        let anotherQueue = DispatchQueue(label: "com.nip.another", qos: .default, attributes: .concurrent)
        
        anotherQueue.async {
            for i in 0 ..< 10 {
                print("🔴",i)
            }
        }
        
        anotherQueue.async {
            for i in 100..<110{
                print("🌘",i)
            }
        }
    }

异步并发，手动执行,必须引用queue

let anotherQueue = DispatchQueue(label: "com.nip.another", qos: .userInitiated, attributes: [.concurrent,.initiallyInactive])
        queue = anotherQueue
        anotherQueue.activate()
        
        anotherQueue.async {
            for i in 0 ..< 10 {
                print("🎾",i)
            }
        }
        
        anotherQueue.async {
            for i in 100..<110{
                print("🏐",i)
            }
        }
        anotherQueue.async {
            for i in 100..<110{
                print("🏉",i)
            }
        }

延迟执行

print(Date())
        
        let queue = DispatchQueue(label: "com.nip.delay", qos: .userInitiated)
        
        queue.asyncAfter(deadline: .now() + 3) { 
            print("⚽️",Date())
        }

任务项 DispatchWorkItem

let workItem = DispatchWorkItem {
        for i in 0 ..< 10 {
            print("🔴",i)
        }
    }

执行任务项

let queue = DispatchQueue(label: "com.nip.queue")
queue.async(execute: workItem)

全局队列

DispatchQueue.global()

 public class func global(qos: DispatchQoS.QoSClass = default) -> DispatchQueue

主队列

DispatchQueue.main

常用的姿势

DispatchQueue.global().async { 
            // 子线程执行
            DispatchQueue.main.async(execute: { 
                // 主线程执行
            })
        }

队列组：实现某些任务执行完了，再去执行相应的任务

DispatchGroup
enter() leave() 一定要对应

let group = DispatchGroup()
group.enter()
DispatchQueue.global().async {
    group.leave()
    for i in 0..<10{
        print(" 🏐 ",i)
    }
}

group.enter()
DispatchQueue.global().async { 
    for i in 100..<110{
        print(" 🏉 ",i)
    }
    group.leave()
}

group.notify(queue: DispatchQueue.main) { 
    for i in 1000..<1010 {
        print(" 🚀 ",i)
    }
}