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iOS Swift Closures Functions as First Class Citizens Higher Order Functions

Posted by Robin Malhotra
Robin Malhotra
14,883 Points

Working in Xcode, not in challenge.

Here's my code that's working with the simulator.

  func differenceBetweenNumbers(a: Int, b:Int) -> (Int)
    {
        return a - b
    }

    func mathOperation (operation:(Int,Int)->Int,a:Int,b:Int)->(Int)
    {
        return operation(a,b)
    }
    let difference = mathOperation(differenceBetweenNumbers,a: 4,b: 2)

1 Answer

Jhoan Arango
Jhoan Arango
14,575 Points

Hello

Simple fix.. take the () off your return.

    func mathOperation (operation:(Int,Int) -> Int, a:Int, b:Int) -> Int {
        return operation(a,b)
    }
Robin Malhotra
Robin Malhotra
14,883 Points

Wait, what? I still don't get how that makes a difference. I mean, differenceBetweenNumbers has brackets on the return type.

Jhoan Arango
Jhoan Arango
14,575 Points

It does not make sense, I know that in Xcode does work, but for some reason on the challenge if you use the () on the return it does not pass the challenge. I knew you had that mistake because I have seen it a million times on other students asking the same question, and they happen to pass the challenge without em. Also I just notice something else that won't let your challenge pass..

Take the parameter names off when calling the function

 let difference = mathOperation(differenceBetweenNumbers, 4,  2)
  • Note: The syntax for swift when doing a return should look like this (Int, Int) -> Int No parenthesis should surround the return type.

Good luck ~