unexpected non-void return value in void function

问题

Below is my code. I'm learning closures. I'm getting an error that my function would not return a value. Can someone help?

func operationOnNumbers(_ a: Int, _ b: Int, operation: (Int, Int) -> Int) {
    let result = operation(a, b)
    print(result)
    return result
}

let addClosure = {(a: Int, b: Int) in
    a + b
}

operationOnNumbers(5, 7, operation: addClosure)

回答1:

Use this modified code as you have missed return type in the function ( -> Int)

func operationOnNumbers(_ a: Int, _ b: Int, operation: (Int, Int) -> Int) -> Int{

    let result = operation(a, b)
    print(result)
    return result
}

let addClosure = {(a: Int, b: Int) in
    a + b
}

operationOnNumbers(5, 7, operation: addClosure)

来源：https://stackoverflow.com/questions/46612620/unexpected-non-void-return-value-in-void-function