Swift活用下面的三组枚举,你可能会少自定义一些枚举

前面几个模式scaleToFill/scaleAspectFit/scaleAspectFill经常会在对于图片的控制上的时候,后的位置关系其实我们对于一些关系定义的时候就可以使用了.

extension UIView { 
    public enum ContentMode : Int {
    
            
            case scaleToFill
    
            case scaleAspectFit // contents scaled to fit with fixed aspect. remainder is transparent
    
            case scaleAspectFill // contents scaled to fill with fixed aspect. some portion of content may be clipped.
    
            case redraw // redraw on bounds change (calls -setNeedsDisplay)
    
            case center // contents remain same size. positioned adjusted.
    
            case top
    
            case bottom
    
            case left
    
            case right
    
            case topLeft
    
            case topRight
    
            case bottomLeft
    
            case bottomRight
    }

}

纵向抑或横向,我已经看见太多的自定义控件中定义这个枚举,孰不知其实系统早就有了.

extension NSLayoutConstraint {

    public enum Axis : Int {

        case horizontal

        case vertical
    }
}

一般倒角的函数会使用这个枚举,其实这个枚举不仅在于使用,更是告诉我们如何定义一个有做个选项的枚举的范例(使用OptionSet协议).

public struct UIRectCorner : OptionSet {

    public init(rawValue: UInt)

    
    public static var topLeft: UIRectCorner { get }

    public static var topRight: UIRectCorner { get }

    public static var bottomLeft: UIRectCorner { get }

    public static var bottomRight: UIRectCorner { get }

    public static var allCorners: UIRectCorner { get }
}