Question

    private enum Operation {
        case BinaryOperation((Double, Double) -> Double)
        case UrinaryOperation((Double) -> Double)
    }
    let plus = Operation.BinaryOperation({$0 + $1})
    let minus = Operation.BinaryOperation({$0 - $1})
    let multiply = Operation.BinaryOperation({$0 * $1})
    let divide = Operation.BinaryOperation({$0 / $1})


    plus(3.0,2.0)

但是，我收到以下错误：

MyPlayground.playground：5：13：错误：无法调用非功能类型的值＆＃39;操作＆＃39; 加（3.0,2.0） ~~~~ ^

Answer 1

您尝试执行的操作的正确语法是：

if case let Operation.BinaryOperation(operation) = plus {
    operation(3.0, 2.0) // results in 5.0
}

您需要获取枚举的相关值。

请注意，您的闭包可以简化为

let plus = Operation.BinaryOperation(+)
let minus = Operation.BinaryOperation(-)
let multiply = Operation.BinaryOperation(*)
let divide = Operation.BinaryOperation(/)

枚举和封闭组合

1 个答案: