swift - 如何从选项集中删除成员

Question

我正在 Xcode 8 的 iOS Playground 中尝试此操作，但它不起作用:

struct Direction: OptionSet {
    let rawValue: UInt8
    static let none = Direction(rawValue: 0)
    static let up = Direction(rawValue: 1 << 0)
    static let left = Direction(rawValue: 1 << 1)
    static let down = Direction(rawValue: 1 << 2)
    static let right = Direction(rawValue: 1 << 3)
    static let all = [up, left, down, right]
}

var directions = Direction.all
directions.remove(.up)    // Error: Missing argument label 'at:' in call

Apple's documentation表明我应该能够

"...to add or remove members from an instance of your custom option set type."

文档引用了 remove() 函数，但这不起作用。我做错了什么？

Answer 1

尝试更改 all 的声明:

static let all: Direction = [.up, .left, .down, .right]