Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

iOS Swift Closures Functions as First Class Citizens Higher Order Functions

scott harris
PLUS
scott harris
Courses Plus Student 23,789 Points

why do these things never work!!!

I know this is right and have tested it in a playground.. wasting hours.. please fix this

/** 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(mathOp: (Int, Int) -> Int, a: Int, b: Int) -> (Int) { return mathOp(a, b) }

let difference = mathOperation(differenceBetweenNumbers, 10, 20)

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

let difference = mathOperation(differenceBetweenNumbers, 10, 20)
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Same here. It would be nice to know why the code above is not considered correct. Here is my code, just for the records. It is (basically) the same as @scottharris4

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

let difference = mathOperation(differenceBetweenNumbers, 10, 8)
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

I think in this particular case it is just the code check. Others had the same problems, although the code works as expected in playground. It seems that removing the parenthesis from the mathOperation return type does the trick. Change your code from

-> (Int)

to

-> Int

So again, it wasn't a mistake you made ;)

1 Answer

scott harris
PLUS
scott harris
Courses Plus Student 23,789 Points

Martin Wildfeuer Your the man!! thanks.. i tried so many nonsense things.. i guess i didn't try that... thanks again!!