如何擴展此UIColor十六進制函數以包含alpha？

Question

如何在此UIColor擴展名中包含alpha？

extension UIColor { 

    convenience init(hex:Int) { 
     self.init(red:(hex >> 16) & 0xff, green:(hex >> 8) & 0xff, blue:hex & 0xff) 
    } 
} 

Answer 1

首先，UIColor沒有任何可以取整數的初始值設定項。我假設你有另一個類似於this的擴展。您必須添加對alpha的支持

// we cannot name the param "alpha" because of a name collision 
convenience init(red: Int, green: Int, blue: Int, a: Int = 255) { 
    self.init(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: CGFloat(a)/255) 
} 

convenience init(hex:Int) { 
    self.init(red:(hex >> 16) & 0xff, green:(hex >> 8) & 0xff, blue:hex & 0xff, a:(hex >> 24) & 0xff) 
} 

（假設alpha是第一個組件）。

如果你想阿爾法只是一個附加的十進制數

convenience init(red: Int, green: Int, blue: Int, a: CGFloat = 1.0) { 
    self.init(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: a) 
} 

convenience init(hex:Int, a: CGFloat = 1.0) { 
    self.init(red:(hex >> 16) & 0xff, green:(hex >> 8) & 0xff, blue:hex & 0xff, a: a) 
}