相关疑难解决方法(0)

我有两节课,Shape和Square

class Shape {
    var numberOfSides = 0
    var name: String
    init(name:String) {
        self.name = name
    }
    func simpleDescription() -> String {
        return "A shape with \(numberOfSides) sides."
    }
}

class Square: Shape {
    var sideLength: Double

    init(sideLength:Double, name:String) {
        super.init(name:name) // Error here
        self.sideLength = sideLength
        numberOfSides = 4
    }
    func area () -> Double {
        return sideLength * sideLength
    }
}

通过上面的实现,我得到错误:

property 'self.sideLength' not initialized at super.init call
    super.init(name:name)

为什么我必须self.sideLength在打电话前设置super.init？

我无法将init方法添加到以下UIViewController类.我需要在init方法中编写一些代码.我必须编写init(编码器)方法吗？即使我添加编码器和解码器方法,我仍然会遇到错误.我也尝试使用没有任何参数的init方法,但这似乎也不起作用.

class ViewController: UIViewController {

    var tap: UITapGestureRecognizer?

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?)   {
        super.init(nibName: nil, bundle: nil)
        tap = UITapGestureRecognizer(target: self, action: Selector("handleTap:"))
    }

...
...
}

如果我调用不带参数的super.init()方法,则错误为"必须调用超类的指定初始化程序",如果我传递参数nib和bundle,则错误为"必需的初始化程序初始化程序(编码器)".

即使我添加init(编码器)和init(解码器)它也不起作用.