原始閉包代碼：

httpTools?.loadData({ (jsonDict : String) in
        self.view.backgroundColor = UIColor.red
        })

方案一

  ###  在閉包前面添加:weak var weakSelf : ViewController? = self

weak var weakSelf : ViewController? = self
        httpTools?.loadData({ (jsonDict : String) in
        weakSelf?.view.backgroundColor = UIColor.red
        })

方案二

    ### self的使用為可選項(xiàng)

httpTools?.loadData({[weak self] (jsonDict : String) in
            self?.view.backgroundColor = UIColor.red
        })

方案三

### [unowned self] ,該方法相當(dāng)于OC中的（unsafe_unretained）當(dāng)引用對(duì)象被釋放的時(shí)候會(huì)產(chǎn)生野指針

 httpTools?.loadData({[unowned self] (jsonDict : String) in
            self.view.backgroundColor = UIColor.red
        })