Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Swift Closures Functions as First Class Citizens Higher Order Functions

Andrei K
Andrei K
7,601 Points
Posted by Andrei K
Andrei K
7,601 Points

Having trouble returning a math operation inside this function

Hello, I'm having a spot of trouble here. I took a look at the Swift docs as well as the project files for the past few lessons but couldn't figure anything out. Might be a silly mistake but any help?

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
}

// Enter your code below
func mathOperation(differenceBetweenNumbers: Int, x: Int, y: Int) -> (Int) {
  return differenceBetweenNumbers(x, y)
}

1 Answer

Chase Marchione
Chase Marchione
155,055 Points
Chase Marchione
Chase Marchione
155,055 Points

Hi Andrei,

func mathOperation(differenceBetweenNumbers: (Int, Int) -> Int, x: Int, y: Int) -> Int {
  return differenceBetweenNumbers(x, y)
}

1) When declaring mathOperation, we're sticking with the same type... the (Int,Int) -> Int... as differenceBetweenNumbers. We're referencing the differenceBetweenNumbers func itself.

2) The second and third parameters, which we have named x and y, are of type Int. x and y will serve as the two input values (which were previously named a and b) that the differenceBetweenNumbers func needs.

Thus, the mathOperation func has the differenceBetweenNumbers function as an argument. Then, we supply the values needed for that func to do its job.

Hope this helps!