Swift中的UIColor扩展错误

Question

我有这个扩展名:

extension UIColor {
    func rgba(r: Int, g: Int, b: Int, a: Float) -> UIColor {
        return UIColor(red: r/255, green: g/255, blue: b/255, alpha: a)
    }    
}

这给了我一个错误信息:Extra argument 'green' in call

我不明白为什么会发生这种情况，可能是xcode 6 beta 4或swift中的错误。

Answer 1

这是因为你传递了错误类型的所有参数:r/255, g/255, b/255是Integer, a是Float，但是UIColor的init方法接受CGFloat作为4个参数

将代码修改为:

func rgba(r: Int, g: Int, b: Int, a: Float) -> UIColor {
    let floatRed = CGFloat(r) / 255.0
    let floatGreen = CGFloat(g) / 255.0
    let floatBlue = CGFloat(b) / 255.0
    return UIColor(red: floatRed, green: floatGreen, blue: floatBlue, alpha: CGFloat(a))
}

Answer 2

extension UIColor {
    convenience init(r: Int, g:Int , b:Int , a: Int) {
        self.init(red: CGFloat(r)/255, green: CGFloat(g)/255, blue: CGFloat(b)/255, alpha: CGFloat(a)/255)
    }
}
let myColor = UIColor(r: 255 , g: 255, b: 255, a: 255)

Answer 3

试试这个:

extension UIColor {
    class func rgba(r: Int, g: Int, b: Int, a: Float) -> UIColor {
        return UIColor(red: r/255, green: g/255, blue: b/255, alpha: a)
    }     
}