如何子类化一个UILabel在swift与字母间距设置为1.5使用NSKernAttribute

Question

我试图子类一个UILabel，使它有一个默认的字距设置为1.5然后我将在我的应用中使用它和多个标签。目标是有默认的kern设置开箱，这样我就可以避免重复的代码在所有的地方，标签也设置为属性和常规文本的混合例子:

@IBoutlet weak var myLabel: CustomeLabelWithKern!
myLabel.attributedText = myAttributedText
@IBOutlet weak var myOtherLabelInADifferentViewController: CustomeLabelWithKern!
myOtherLabelInADifferentViewController.text "Foo Bar"

这两个标签的kern都应该是1.5

这是我目前看到的

class CustomLabel: UILabel {
   var kerning: CGFloat = 1.5
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setKerning(kerning)
    }
    private func setKerning(kern: CGFloat) {
        guard let text = self.text else { return }
        let range = NSRange(location: 0, length: text.characters.count)
        let mutableString = NSMutableAttributedString(attributedString: attributedText ?? NSAttributedString())
        mutableString.addAttribute(NSKernAttributeName, value: kern, range: range)
        attributedText = mutableString
    }
} 

Answer 1

这是我到目前为止所拥有的，我想我现在会使用这个解决方案，如果有人想出一个更好的，我会很乐意尝试，以及

class CustomLabel: UILabel {
    static var kerning: CGFloat = 1.5
    override func awakeFromNib() {
       super.awakeFromNib()
       setKerning(CustomLabel.kerning)
    }
    func setKerning(kern: CGFloat) {
        let text = self.text ?? ""
        let range = NSRange(location: 0, length: text.characters.count)
        let mutableString = NSMutableAttributedString(attributedString: attributedText ?? NSAttributedString())
        mutableString.addAttribute(NSKernAttributeName, value: kern, range: range)
        attributedText = mutableString
    }
}

我可以在我的viewController

中这样使用

mylabel.text = "Hello World!" // this should be set to 1.5 by default but what if i am setting my label dynamically? 
mylabel.setKerning(1.5) // Here i am passing the value so if the label is set dynamically set it will have correct spacing 
// This also works if some of my labels have attributed text 
myAttibutedLabel.attributedText = myAttributedText
myAttributedLabel.setKerning(1.5)

我认为这可以减少到只是一个扩展的UILabel类Like so

extension UILabel {
    func setKerning(kern: CGFloat) {
        let text = self.text ?? ""
        let range = NSRange(location: 0, length: text.characters.count)
        let mutableString = NSMutableAttributedString(attributedString: attributedText ?? NSAttributedString())
        mutableString.addAttribute(NSKernAttributeName, value: kern, range: range)
        attributedText = mutableString
   }
}

Answer 2

如何像这样子类化UILabel:

class TestKerningLabel: UILabel {
 func addKerning(kerningValue: Double) {
    let attributedString = self.attributedText as! NSMutableAttributedString
    attributedString.addAttribute(NSKernAttributeName, value: kerningValue, range: NSMakeRange(0, attributedString.length))
    self.attributedText = attributedString
 }
}

然后在VC中使用:

let testLabel = TestKerningLabel()
testLabel.attributedText = NSAttributedString(string: "test")
testLabel.addKerning(kerningValue: 1.5)
view.addSubview(testLabel)