iOS 自定义初始化问题，如何设置默认初始化方法？

Question

我有一个自定义 UILabel class。

class CustomLabel: UILabel{


    init(_ title: String = "Star"){
        super.init(frame: CGRect.zero)
        text = title
    }

    override init(frame: CGRect) {
        fatalError("Not Implemented")
    }


    required init?(coder aDecoder: NSCoder) {
        fatalError("Not Implemented")
    }


}

我这样叫就可以了

let head = CustomLabel("Front")

这样叫不好

let lhs = CustomLabel()

Xcode 报告：未实施，程序在此处停止。

override init(frame: CGRect) {
     fatalError("Not Implemented")
}

显然let lhs = CustomLabel()调用方法override init(frame: CGRect) {,

如何使 init(_ title: String = "Star"){ 默认？

即。让Xcode先找到。

Answer 1

删除您实施的其他 init 并根据需要设置您的

class CustomLabel: UILabel {

    required init(_ title: String = "Star"){
        super.init(frame: CGRect.zero)
        text = title
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

}

let label1 = CustomLabel()
print(label1)

这有效并使用预期的初始化

编辑：

Bastian 在他们的回答中提供了一个有用的 link，但后来将其删除。

link：Adding Swift Convenience Initializers

来自 link 的有用片段（以防 link 中断）：

Designated or Convenience?

First a recap on the two types of initializer:

A designated initializer is the primary initializer for a class. It must fully initialize all properties introduced by its class before calling a superclass initializer. A class can have more than one designated initializer.

A convenience initializer is a secondary initializer that must call a designated initializer of the same class. It is useful when you want to provide default values or other custom setup. A class does not require convenience initializers.

The Three rules

With that clear you need to remember three rules for designated and convenience initializers for class types:

A designated initializer must call a designated initializer from the immediate superclass.

A convenience initializer must call another initializer from the same class.

A convenience initializer must ultimately call a designated initializer.

What does this mean for us? In simple terms, do not call super from your convenience initializer. Call another initializer (convenience or designated) from the same class.

iOS 自定义初始化问题，如何设置默认初始化方法？

iOS custom init issue, how to set the default init method?

init

ios

swift