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iOS Swift Closures Functions as First Class Citizens Higher Order Functions

Lauren Hibbs
Lauren Hibbs
1,872 Points
Posted by Lauren Hibbs
Lauren Hibbs
1,872 Points

Higher Order Functions - works in Xcode but not on treehouse

I can't for the life of me figure out why this code will not work for the challenge task. It wrote it in playground as well and it works perfectly there. The error just says to make sure I am assigning the result to a constant named difference and check that the parameters are correct. Thanks.

higherOrderFunctions.swift 
/** 
  For this code challenge, let’s define a math operation as a function that 
  carries out some work on two integers and returns an integer as well. An 
  example is the function below, `differenceBetweenNumbers`, which takes two 
  integers and calculates the difference between the numbers. After calculating, 
  it returns the difference.
*/
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, 10 , 7)

1 Answer

Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Hello:

Your code looks good so far, but for some reason the compiler won't let it pass if you have the parenthesis on the returns.

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

// By taking the parenthesis out from the return, it will let the compiler pass your challenge. 

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

let difference = mathOperation(differenceBetweenNumbers, 10 , 7)

Good luck, hope this helps.