具有存储枚举的条件枚举开关 [英] Conditional enum switch with stored enum

问题描述

我希望这段代码可以正常工作。

I'd like this code to work.

我有一个枚举，其中Direction.Right需要一个距离参数。

I have an enum where the case Direction.Right takes a distance parameter.

enum Direction {
    case Up
    case Down
    case Left
    case Right(distance: Int)
}

现在另一个可以采用Direction参数的枚举。

Now another enum that can take a Direction parameter.

enum Blah {
    case Move(direction: Direction)
}

let blah = Blah.Move(direction: Direction.Right(distance: 10))

当我打开 Blah 枚举我想要有条件地打开Move.Right这样...

When I switch on the Blah enum I want to be able to conditionally switch on the Move.Right like this...

switch blah {
case .Move(let direction) where direction == .Right:
    print(direction)
default:
    print("")
}

但是我收到错误...

But I get the error...

二进制运算符'=='不能应用于歌剧方向和_类型的数组

binary operator '==' cannot be applied to operands of type 'Direction' and '_'

有没有办法？ / p>

Is there a way to do this?

推荐答案

其实很简单：）

    case .Move(.Up):
        print("up")
    case .Move(.Right(let distance)):
        print("right by", distance)

您的代码

    case .Move(let direction) where direction == .Right:

不编译，因为 == 仅在
枚举中定义，而没有关联值。

does not compile because == is defined by default only for enumerations without associated values.

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