swift-closure use and solve circular reference problems

The closure in Swift is used in the reference OC, basically consistent

//Closure Type First write (parameter list)--(return value type)Func LoadData (callBack: (jsondata:string)()) {Dispatch_async (Dispatch_get_global_queue (0,0) {print ("Network request \ (Nsthread.currentthread ())") Dispatch_sync (Dispatch_get_main_queue (), {print ("get to Data \ (Nsthread.currentthread ())") CallBack (jsondata:"Data")            })        }    }

There are three ways to resolve a closed loop reference in Swift:

1. Like OC, use weak (OC is __weakself)

2. Simplify the first method of tools?. LoadData ({[Weak self] (jsondata) in}) here self needs unpacking (recommended)

3. Simplify the first method of tools?. LoadData ({[unowned self] (jsondata) (}) This method crashes when self is empty

swift-closure use and solve circular reference problems