如何在Swift中使用枚举内部的函数选择枚举值？

enum Operation {
    case addition
    case subtraction
    case multiplication
    case division
    
    func performOperation(a: Int, b: Int) -> Int {
        switch self {
        case .addition:
            return a + b
        case .subtraction:
            return a - b
        case .multiplication:
            return a * b
        case .division:
            return a / b
        }
    }
}

let op: Operation = .addition
let result = op.performOperation(a: 5, b: 3)
print(result) // 输出：8