Question

基本上我有一个功能。我还有另一个具有完成处理程序的函数。在继续第一个功能的行之前，我需要第二个功能的结果。我尝试了Dispatch小组，但是没有用。

    func parseData(from json: [String: Any) -> Val {
      var a //some values I got from parsing that I NEED for B
      var anotherVariable
      B(a) { result in 
         anotherVariable = result
      }
      var otherVar = anotherVariable[0]
      return Val(a, anotherVariable, otherVar) // this is a struct                                               
      //returned
    }

    func B(_ a: a, completion: @escaping ([Res]) -> Void) {
      let group = DispatchGroup()
      var res = [Res]()

      SomeotherFunc(a, completion: { resp in
      res = resp
      group.leave()
    })
      group.notify(queue: .main) {
        completion(res)
      }
    }

Answer 1

尝试此解决方案。它正在工作

func parseData(from json: [String: Any) -> Val {

        var a //some values I got from parsing that I NEED for B
        var anotherVariable

        let group = DispatchGroup()
        group.enter()
        B(a) { result in
            anotherVariable = result
            group.leave()
        }

        group.wait()
        var otherVar = anotherVariable[0]
        return Val(a, anotherVariable, otherVar) // this is a struct
        //returned
    }

    func B(_ a: a, completion: @escaping ([Res]) -> Void) {
        SomeotherFunc(a, completion: { resp in
            completion(res)
        })
    }

Answer 2

不要那样做。

请学习了解异步数据处理的工作原理，并在parseData中添加另一个完成处理程序。而且您在DispatchGroup中滥用B。顾名思义，它仅对异步调用的 group 组有用，例如在循环中

func parseData(from json: [String: Any], completion: @escaping (Val) -> Void) {
    var a //some values I got from parsing that I NEED for B
    var anotherVariable
    B(a) { result in
        anotherVariable = result
        completion(Val(a, anotherVariable, anotherVariable[0]))
    }
}

func B(_ a: a, completion: @escaping ([Res]) -> Void) {
    var res = [Res]()

    SomeotherFunc(a) { resp in
        res = resp
        completion(res)
    })
}

在继续执行之前使函数执行

2 个答案: