ios - 如何在 Swift 中优化链式异步请求

Question

我有像 A->B->C 这样的请求链接代码，我正在使用 URLSession 所有请求都按正确的顺序和预期的行为完成。但我想知道如何优化这个链接，因为它看起来很复杂而且不可重用。我正在寻找如何以更灵活的方式进行这种链接的建议。

我的代码:

URLSession.shared.dataTask(with: URLRequest(url: URL(string: "first")!)){ data , res , err in
    let second = URLRequest(url: URL(string: "second")!)
    URLSession.shared.dataTask(with: second){ data , res , err in
        let third = URLRequest(url: URL(string: "second")!)
        URLSession.shared.dataTask(with:third){ data , res , err in
         }.resume()
    }.resume()
}.resume()

Answer 1

实际上，您可以像下面这样使用 OperationQueues 来使用依赖项:

func operationQueueWithBlockandCancel(){

    let mainQueue = OperationQueue.main

    let operationBlock1 = BlockOperation()
    let operationBlock2 = BlockOperation()
    let operationBlock3 = BlockOperation()


    operationBlock1.addExecutionBlock {
       //Any task
    }

    operationBlock2.addExecutionBlock {
       //Any task
    }


    operationBlock3.addExecutionBlock {
        //Any task
    }

    //Add dependency as required
    operationBlock3.addDependency(operationBlock2)
    operationBlock2.addDependency(operationBlock1)

    opQueue.addOperations([operationBlock2,operationBlock1,operationBlock3,], waitUntilFinished: false)

}