Swift 基本语法（十一）— 泛型、多线程

//泛型编程是一种面向算法的多态技术
//协议关联类型 - 相当于泛型 associatedtype.  协议不支持泛型指定
/** 当协议里不知道该存储什么类型时， 使用一个关联类型占位的意思 */
protocol Container {
    associatedtype ItemType: Equatable //也可以给关联类型遵循协议
    mutating func append(_ item: ItemType)
    var count: Int {get}
    subscript(i: Int) -> ItemType {get}
}

extension Container {
    subscript<Indices: Sequence>(indice: Indices) -> [ItemType] where Indices.Iterator.Element == Int {
        var result = [ItemType]()
        for index in indice {
            result.append(self[index])
        }
        return result
    }
}

多线程

//多线程 Thread两种方法
for i in 0..<10 {
    Thread.detachNewThread {
        print(i)
    }
}

class TestThread {
    func threadFunction() -> Void {
        let thread = Thread(target: self, selector: #selector(threadFunc), object: nil)
        thread.start()
    }
    
    @objc func threadFunc() {
        print("Thread")
    }
}

//Operation  OperationQueue 简单使用。  和OC的很类似， 其他使用方法参考OC
class OperationClass {
    func blockOperation() -> Void {
        let op = BlockOperation {
            sleep(2)
            print("BlockOperation")
        }
        op.completionBlock = { [weak self] in
            print("Test + \(self)")
        }
        
        let op2 = BlockOperation(block: {[weak self] in
            sleep(1)
            self?.opFunc()
        })
        
        //operation执行完的回调
        op2.completionBlock = {
            print("都执行完了")
        }
        
        let queue = OperationQueue()
        queue.addOperation(op)
        queue.addOperation(op2)
    }
    
    func opFunc() -> Void {
        print("laile")
    }
}
let opClass = OperationClass()
opClass.blockOperation()
print("主线程开始执行")

//也可以继承自Operation
class MyOperation: Operation {
    override func main() {
        sleep(1)
        print("Custom Operation")
    }
}

GCD

//GCD
//这样简单创建的是串行队列
let serialQueue = DispatchQueue(label: "SerialQueue")

/**label： 队列标志名
 qos：一般选默认即可，  有background等模式
 attributes：指定串行还是b并发队列
 autoreleaseFrequency： 一般选继承类型即可inherit
 target：目标队列，可以不设置，系统会自动添加到目标队列里
 */
let queue = DispatchQueue(label: "MyQueue", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)
queue.sync {
    sleep(1)
    print("in queue sync")
}
print("after invoke queue method")
queue.async {
    sleep(1)
    print("in queue async")
}
print("after invoke queue method")
queue.asyncAfter(deadline: DispatchTime.now() + 1) {
    print("asyn after")
}

//GCD Group
let group = DispatchGroup()
let queue1 = DispatchQueue(label: "myQueue", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)
group.enter()
queue1.async {
    sleep(1)
    print("1111")
    group.leave()
}
group.enter()
queue1.async {
    print("22222")
    group.leave()
}
print("enter 完成")
//group.wait()
print("wait 是阻塞的，这个最后执行")

group.notify(queue: queue1) {
    print("12完成了")
}
print("Notify 是不阻塞的, 会先执行")

//DispatchSource - Timer
var seconds = 10
let queue = DispatchQueue(label: "MyQueue", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)

let timer = DispatchSource.makeTimerSource(flags: DispatchSource.TimerFlags.init(), queue: queue)
timer.schedule(deadline: DispatchTime.now(), repeating: 1)
timer.setEventHandler {
    seconds -= 1
    if seconds < 0 {
        timer.cancel()
    }else {
        print(seconds)
    }
}
timer.resume()

//g多线程保证数组读写完全
class SafeArray {
    let queue1 = DispatchQueue(label: "queue1", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)
    let queue2 = DispatchQueue(label: "queue2", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)
    
        let arrayQueue = DispatchQueue(label: "arrayQueue", qos: DispatchQoS.default, attributes: DispatchQueue.Attributes.concurrent, autoreleaseFrequency: DispatchQueue.AutoreleaseFrequency.inherit, target: nil)
    
    var largeArray = Array(0...10000)
    
//    let lock = NSLock()
//    func getLastItem() -> Int? {
//        lock.lock()
//        var temp = 0
//        if largeArray.count > 0 {
//            temp = largeArray[largeArray.count - 1]
//        }
//        lock.unlock()
//        return temp
//    }
//
//    func removeLastItem() -> Void {
//        lock.lock()
//        largeArray.removeLast()
//        lock.unlock()
//    }
    
    //更高效的获取方法
    func getLastItem() -> Int {
        arrayQueue.sync { () -> Int in
            var temp = 0
            if largeArray.count > 0 {
                temp = largeArray[largeArray.count - 1]
            }
            return temp
        }
    }
    //栅栏函数
    func removeLastItem() -> Void {
        let workItem = DispatchWorkItem(qos: DispatchQoS.default, flags: DispatchWorkItemFlags.barrier) {
            self.largeArray.removeLast()
        }
        arrayQueue.async(execute: workItem)
    }
    
    
    func testSafeArray() -> Void {
        queue1.async {
            for _ in 0...10000 {
                let index = self.getLastItem()
                print(index as Any)
            }
        }
        queue2.async {
            for _ in 0...10000 {
                self.removeLastItem()
            }
        }
    }
}

let safeArr = SafeArray()
safeArr.testSafeArray()

//栅栏函数使用
DispatchQueue.global().async(group: group, qos: DispatchQoS.default, flags: DispatchWorkItemFlags.barrier) {
        
    }