Question

很抱歉，如果这是一个基本问题，但我无法在任何地方找到解决方案。我想在Init之外的函数中初始化类属性，并且只从构造函数内部调用它。我这样做是为了避免代码重复，因为当前版本看起来像这样：

public class WifiNameDisplay: UIView {
    var wifiImageView: UIImageView
    var networkName: UILabel
    public var networkSSID: String {
        didSet {
            networkName.text = networkSSID
            adjustSizeToContent()
        }
    }

    override public init(frame: CGRect) {
        networkSSID = "NETWORK"
        wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
        networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))

        super.init(frame: frame)
    }


    convenience public init() {
        self.init(frame: CGRect.zero)
    }

    required public init(coder aDecoder: NSCoder) {
        networkSSID = "NETWORK"
        wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
        networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))

        super.init(coder: aDecoder)!
    }
}

我想把它改成这样的东西：

public class WifiNameDisplay: UIView {
    var wifiImageView: UIImageView
    var networkName: UILabel
    public var networkSSID: String {
        didSet {
            networkName.text = networkSSID
            adjustSizeToContent()
        }
    }

    override public init(frame: CGRect) {
        initDefaultValues()
        super.init(frame: frame)
    }


    convenience public init() {
        self.init(frame: CGRect.zero)
    }

    required public init(coder aDecoder: NSCoder) {
        initDefaultValues()
        super.init(coder: aDecoder)!
    }

    func initDefaultValues() {
        networkSSID = "NETWORK"
        wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
        networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))
    }
}

问题是编译器不允许这样做，在super.init初始化self之前调用“在方法调用'initDefaultValues'中使用'self'”。我想要的甚至可能，还是我被迫使用重复代码？

Answer 1

如果您将属性声明为隐式解包的选项，那么您可以在调用超类init函数后初始化它们 -

public class WifiNameDisplay: UIView {
    var wifiImageView: UIImageView!
    var networkName: UILabel!
    public var networkSSID: String! {
        didSet {
            networkName.text = networkSSID
          //  adjustSizeToContent()
        }
    }

    override public init(frame: CGRect) {

        super.init(frame: frame)
        initDefaultValues()
    }


    convenience public init() {
        self.init(frame: CGRect.zero)
    }

    required public init(coder aDecoder: NSCoder) {

        super.init(coder: aDecoder)!
        initDefaultValues()
    }

    func initDefaultValues() {
        networkSSID = "NETWORK"
        wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
        networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))
    }
}

Answer 2

据我所知，有两种方法。在定义值时初始化值：

public class WifiNameDisplay: UIView {
    var wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
    var networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))
    public var networkSSID = "Network"
}

但这对您不起作用，因为networkName在此范围内不了解wifiImageView，因此无法为其找到正确的框架。我发现这对于设置偏移量，字符串常量等简单用例很有用，但是不建议将其用于UI元素。

其他方法是使变量（隐式解包）可选，并在initDefaultValues之后调用super.init：

public class WifiNameDisplay: UIView {
    var wifiImageView: UIImageView!
    var networkName: UILabel!
    public var networkSSID: String! {
        didSet {
            networkName.text = networkSSID
        }
    }

    override public init(frame: CGRect) {
        super.init(frame: frame)
        initDefaultValues()
    }

    required public init(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)!
        initDefaultValues()
    }

    func initDefaultValues() {
        networkSSID = "NETWORK"
        wifiImageView = UIImageView(image: UIImage(named: "wifi_icon.png")!)
        networkName = UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400, height: wifiImageView.frame.size.height)))
    }
}

Answer 3

将要在init函数之外初始化的属性更改为lazy属性：

lazy var  networkName:UILabel = { return UILabel(frame: CGRect(origin: CGPoint.zero, size: CGSize(width: 400,     
                                  height: self. wifiImageView.frame.size.height)))}()

在Init函数之外初始化类属性

3 个答案: