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Start your free trialjames gamber
7,727 Pointsgenerics in swift 3 challenge task 1 of 1
Generics in Swift 3 Challenge Task 1 of 1
In the editor define a function named map with two generic type parameters, T and U. The function takes two arguments - array of type [T], and transformation of type (T) -> U. The function returns an array of type U.
The goal of the function is to apply the transformation operation on the array passed in as argument to return a new array containing the values transformed. For example given the array [1,2,3,4,5] as first argument, and a square function as the transformation argument, the result should be [1, 4, 9, 16, 25].
func map<T, U>(array: [T], transformation: ([T])->[U])->[U] { return transformation(array) }
func square(array: Array<Int>) ->Array<Int> { var sq : Array<Int> = []
for item in array {
sq.append( item * item )
}
return sq
}
works in payground
but treehouse shows error Bummer! Make sure your second argument has the external name transformation and type (T) -> U
func map<T, U>(array: [T], transformation: ([T])->[U])->[U] {
return transformation(array)
}
func square(array: Array<Int>) ->Array<Int> {
var sq : Array<Int> = []
for item in array {
sq.append( item * item )
}
return sq
}
2 Answers
David Papandrew
8,386 PointsJames,
I kept my notes for this module because I struggled with it and knew that I might need to refer back to the code challenge answers.
Here's the solution that worked for me:
func map<T, U>(array: [T], transformation: (T) -> U) -> [U] {
var transformedArray: [U] = []
for item in array {
let newValue = transformation(item)
transformedArray.append(newValue)
}
return transformedArray
}
func squared(_ number: Int) -> Int {
return number * number
}
Adam Teale
10,989 Pointsyes the question could be a little clearer
james gamber
7,727 Pointsjames gamber
7,727 PointsThanks that works.
I was trying to pass the array to the function, rather than operate on one element of the array with each func call to squared.