Struct Swift结构找不到成员

我有这个结构：

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
}

我试着这样使用它：

class AClass {
    var point:CGPoint!

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

---

我试图将

.None

设置为

var

和

public

，但我似乎不明白这一点。

似乎您试图使用结构的静态成员，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
}

---

如果@Kirsteins的假设是正确的，并且您需要使用struct值作为静态属性，那么有另一种方法可以实现相同的结果，但在我看来是更好的方法：使用enum

但是swift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。幸运的是，swift使我们能够使用字符串文字来指定对，然后将其转换为

CGFloat

：

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

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

此扩展允许我们初始化

CGFloat

，如下所示：

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

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}"
}

有了它，我们可以如下定义枚举：

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

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}"
}

并在代码段中用作：

class AClass {
    var point:CGPoint!

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

---

Daeem，这实际上是我一开始想要的，但我甚至不知道这是可能的，所以我问了一个结构！