Swift Property ‘self.xxx‘ not initialized at super.init call

Swift重写父类的init方法时，报了如下错误。

Property 'self.xxx' not initialized at super.init call

大概意思是在调用父类init方法前，需要给属性赋值。

报错代码

    required init(leftController: UIViewController?, centerController: UIViewController) {
        super.init(nibName: nil, bundle: nil)
        
        self.centerController = centerController
        if (leftController != nil) {
            self.leftController = leftController
        }
    }

修改如下：

    required init(leftController: UIViewController?, centerController: UIViewController) {
        self.centerController = centerController
        if (leftController != nil) {
            self.leftController = leftController
        }
        super.init(nibName: nil, bundle: nil)
    }

See also:
【1】Property ‘self.*’ not initialized at super.init call：https://stackoverflow.com/questions/29890510/property-self-not-initialized-at-super-init-call