斯威夫特结构没有找到成员

Question

我有这样的结构：

struct Direction { 
    let Left = CGPoint(x: -1, y: 0) 
    let Top = CGPoint(x: 0, y: -1) 
    let Right = CGPoint(x: 1, y: 0) 
    let Down = CGPoint(x: 0, y: 1) 

    let TopLeft = CGPoint(x: -1, y: -1) 
    let TopRight = CGPoint(x: 1, y: -1) 
    let DownLeft = CGPoint(x: -1, y: 1) 
    let DownRight = CGPoint(x: 1, y: 1) 

    let None = CGPointZero 
} 

我尝试使用这样的：

class AClass { 
    var point:CGPoint! 

    init() { 
     self.point = Direction.None // Direction.Type does not have a member named 'None' 
    } 
} 

我试图设置.None为var和public但我似乎并不了解这一点。

Answer 1

似乎您正在尝试使用该结构的静态成员，但您只声明了实例成员。将static添加到所有属性。

struct Direction { 
    static let Left = CGPoint(x: -1, y: 0) 
    static let Top = CGPoint(x: 0, y: -1) 
    static let Right = CGPoint(x: 1, y: 0) 
    static let Down = CGPoint(x: 0, y: 1) 

    static let TopLeft = CGPoint(x: -1, y: -1) 
    static let TopRight = CGPoint(x: 1, y: -1) 
    static let DownLeft = CGPoint(x: -1, y: 1) 
    static let DownRight = CGPoint(x: 1, y: 1) 

    static let None = CGPointZero 
} 

Answer 2

如果@ Kirsteins的假设是正确的，你需要为静态属性，那么就实现了同样的结果的另一种方法，可使用结构值，但在我以更好的方式意见：使用枚举。

但是，快速枚举只接受字符，字符串和数字作为原始值，而CGPoint由一对浮点组成。幸运迅速的给我们使用一个字符串指定一对，然后将其转化成CGFloat的能力：

extension CGPoint : StringLiteralConvertible { 
    public static func convertFromStringLiteral(value: StringLiteralType) -> CGPoint { 
     return CGPointFromString(value) 
    } 

    public static func convertFromExtendedGraphemeClusterLiteral(value: StringLiteralType) -> CGPoint { 
     return convertFromStringLiteral(value) 
    } 
} 

这个扩展可以让我们初始化CGFloat如下：

let point: CGPoint = "{1, -3}" 

随着在我们手中，我们可以如下定义枚举：

enum Direction : CGPoint { 
    case Left = "{-1, 0}" 
    case Top = "{0, -1}" 
    case Right = "{1, 0}" 
    case Down = "{0, 1}" 

    case TopLeft = "{-1, -1}" 
    case TopRight = "{1, -1}" 
    case DownLeft = "{-1, 1}" 
    case DownRight = "{1, 1}" 

    case None = "{0, 0}" 
} 

，并在您的代码段使用为：

class AClass { 
    var point:CGPoint! 

    init() { 
     self.point = Direction.None.toRaw() 
    } 
}