设置请求并发数

一、请求超时

// 设置请求最大并发数
URLSessionConfiguration().httpMaximumConnectionsPerHost = xxxx

二、多任务无顺序

• 自动关联

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
    let group = DispatchGroup()
    
    DispatchQueue.global().async(group: group, execute: {
        print("1")
    })
    DispatchQueue.global().async(group: group, execute: {
        print("2")
    })
    DispatchQueue.global().async(group: group, execute: {
        print("3")
    })
    DispatchQueue.global().async(group: group, execute: {
        print("4")
    })
    DispatchQueue.global().async(group: group, execute: {
        print("5")
    })
    DispatchQueue.global().async(group: group, execute: {
        print("6")
    })
    
    group.notify(queue: DispatchQueue.main) {
        print("end")
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
    let block = BlockOperation {
        print("1")
    }
    block.addExecutionBlock {
        print("2")
    }
    block.addExecutionBlock {
        print("3")
    }
    block.addExecutionBlock {
        print("4")
    }
    block.addExecutionBlock {
        print("5")
    }
    block.addExecutionBlock {
        print("6")
    }
    block.addExecutionBlock {
        print("7")
    }
    
    // 监听任务完成
    block.completionBlock = {
        print("end")
    }
    block.start()
}

• 手动关联

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
    let group = DispatchGroup()
    
    group.enter()
    DispatchQueue.global().async {
        print("1")
        group.leave()
    }
    group.enter()
    DispatchQueue.global().async {
        print("2")
        group.leave()
    }
    group.enter()
    DispatchQueue.global().async {
        print("3")
        group.leave()
    }
    group.enter()
    DispatchQueue.global().async {
        print("4")
        group.leave()
    }
    group.enter()
    DispatchQueue.global().async {
        print("5")
        group.leave()
    }
    group.enter()
    DispatchQueue.global().async {
        print("6")
        group.leave()
    }
    
    group.notify(queue: DispatchQueue.main) {
        print("end")
    }
}

三、多任务有顺序

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    
    let block1 = BlockOperation {
        print("1")
    }
    let block2 = BlockOperation {
        print("2")
    }
    let block3 = BlockOperation {
        print("3")
    }
    let block4 = BlockOperation {
        print("4")
    }
    let block5 = BlockOperation {
        print("5")
    }
    block2.addDependency(block1)
    block3.addDependency(block2)
    block4.addDependency(block3)
    block5.addDependency(block4)
    
    block1.start()
    block2.start()
    block3.start()
    block4.start()
    block5.start()
}