Swift:弱引用存储和嵌套 block /闭包

Question

我希望嵌套一个 block /闭包，同时另一个进程像这样从主线程完成

typealias FirstBlock = (jsonDictionary:NSDictionary?,errorCode:NSString?) -> Void

typealias SecondBlock = (complete:Bool?,errorCode:NSString?,dictionary:NSDictionary?) -> Void

• Controller

      func startPoint {
  
          SomeNetworkManager.sharedInstance.firstProcess(self.someDictionary) { (complete, errorCode, dictionary) -> Void in
  
          // I want to get here with a strong reference to these objects in this class only
          print(complete,errorCode,dictionary)
      }
  }
  

• 一些网络管理器

  func firstProcess(dictionary:NSDictionary?, completion:SecondBlock?) {
  
  let request = HTTPRequest.init(requestWithPath:"path", httpMethod: .post) { (jsonDictionary, errorCode) -> Void in
  
      let organisedDictionary:NSMutableDictionary = NSMutableDictionary() 
      // Some processing of the json into a new dictionary
  
      dispatch_async(dispatch_get_main_queue()) {
  
          if errorCode == nil {
  
              completion!(complete:true,errorCode:nil,dictionary:organisedDictionary)
          }
          else {
  
              completion!(complete:false,errorCode:errorCode,dictionary:nil)
          }
      }
  }
  
  request.postDataDictionary = refinementsDictionary as! NSMutableDictionary
  request.request()
  
  }
  

• HTTP 请求

  var processBlock:FirstBlock?
  
  init(requestWithPath path:NSString, httpMethod method:HTTPMethod, andProcessBlock block:FirstBlock) {
  
      super.init()
  
      self.requestURL = NSURL(string:path as String);
      self.responseData = NSMutableData()
      self.processBlock = block
  
      switch (method) {
       case .post:
          self.httpMethod = kPost
          break;
       case .put:
          self.httpMethod = kPut
          break;
       default:
          self.httpMethod = kGet
          break;
      }
  
  }
  
  // An NSURLConnection goes off, completes, I serialise the json and then...
  
  func completeWithJSONDictionary(jsonDictionary:NSDictionary) {
  
      self.processBlock!(jsonDictionary:jsonDictionary,errorCode:nil)
      self.processBlock = nil
  }
  

我遗漏了一些关于 ARC 保留周期的基本知识，因为每次调用其中一个时，我都会遇到内存泄漏..我已经看过了 https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/AutomaticReferenceCounting.html没有喜悦..我认为定义捕获列表是正确的区域，但至于存储 block 以及如何定义它，我不知道我做错了什么。

Answer 1

很可能，您会遇到保留周期，因为完成 block 引用 HttpRequest(可能通过调用对象)，引用完成 block ，例如:

class HttpReference {
    let completion : ()->()

    init(completion:()->()) {
        self.completion = completion
    }
}

class Owner {
    var httpReference : HttpReference?

    func someFunction() {
        httpReference = HttpReference() {
            print(self.httpReference)
        }
    }
}

有两种方法可以打破循环，要么使用unowned引用，要么使用weak引用，两者都非常相似，在这种情况下，规范是通过更改来使用对 self 的无主引用:

func someFunction() {
    httpReference = HttpReference() { [unowned self] in
        print(self.httpReference)
    }
}

现在，self 未被保留，从而打破了保留周期。