闭包：属性声明
private var myFailClosure: ((NSError) -> Void)?
private var mySuccessClosure: ((NSData)->Void)?

方法中声明，挂闭包
func postWithSNS(withUrlString urlStr:String? , params: [String:String]? , failClosure: ((NSError)->Void) , successClosure: ((NSData)->Void) ){

    self.myFailClosure = failClosure
    self.mySuccessClosure = successClosure

downloadMission.postWithSNS(withUrlString: urlString, params: paramDict, failClosure: { (nothing) in

        print("我勒个去 继续")
        
        Assist.showAlert("Can't Quit", comfirmClosure: nil, shower: self)

闭包的实现，
}) { (data) in

            print(data)
            
            
            let jsonData = try! NSJSONSerialization.JSONObjectWithData(data, options: .MutableContainers)

还欠缺一环：
闭包的调用：
在Connection的代理方法中
调用

//下载失败
func connection(connection: NSURLConnection, didFailWithError error: NSError) {
    
    if self.delegate != nil {
        //代理方式
        self.delegate?.download(self, failWithError: error)
    }else if self.myFailClosure != nil {
        //闭包方式
        self.myFailClosure!(error)
    }
    
}

func connectionDidFinishLoading(connection: NSURLConnection) {

    if self.delegate != nil {
        //代理方式
        self.delegate?.download(self, finishWithData: self.receiveData)
    }else if self.myFinishClosure != nil {
        //闭包方式
        self.myFinishClosure!(self.receiveData)
    }
    
}