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iOS Generics in Swift Generic Functions, Parameters and Constraints Generic Functions

Aananya Vyas
Aananya Vyas
20,157 Points
Posted by Aananya Vyas
Aananya Vyas
20,157 Points

confused with the return type.

the question is:

Write a function named duplicate with a single generic type parameter T. The function takes two arguments, item of type T, and numberOfTimes of type Int, and returns an array of type T. The function simply creates an array containing the element duplicated by the number of times specified. For example, calling duplicate(item: 1, numberOfTimes: 4) returns [1, 1, 1, 1].

pl go through the code attached (cant understand how to define the return type.)

generics.swift 
 let arr : T

func duplicate<T>(item : inout T , numberOfTimes: Int) -> arr {

    var i = 0
    for i in numberOfTimes {
        arr[i] = item
        i++
    }
    }
   print(arr)


duplicate(item: &2, numberOfTimes: 2)

8 Answers

Josh Byron
Josh Byron
5,156 Points

Here's the code I used to complete this task. Hope it helps :)

func duplicate <T> (item : T,numberOfTimes: Int)-> [T]{
    var arr : [T] = [T]()
    for _ in 0...(numberOfTimes - 1){
        arr.append(item)
    }
    return arr
}
Randell Pur
Randell Pur
4,934 Points
Randell Pur
Randell Pur
4,934 Points

Could you explain how you came to this answer? It worked for me but I am still confused on how this works.

jc laurent
jc laurent
6,351 Points
jc laurent
jc laurent
6,351 Points

as the very moment you put this -> in your function you'll need the return key if not it will be a simple function with no return key as

func anyfunc() {

}

Qasa Lee
Qasa Lee
18,916 Points
Qasa Lee
Qasa Lee
18,916 Points 
import Foundation
//Write a function named duplicate with a single generic type parameter T. The function takes two arguments, item of type T, and numberOfTimes of type Int, and returns an array of type T.
//The function simply creates an array containing the element duplicated by the number of times specified. For example, calling duplicate(item: 1, numberOfTimes: 4) returns [1, 1, 1, 1].

func duplicate<T>(item: T, numberOfTimes: Int) -> Array<T> {
    var a: [T] = []
    for _ in (1...numberOfTimes) {
        a.append(item)
    }
    return a
}

//duplicate(item: 1, numberOfTimes: 4)
//duplicate(item: "Hi~", numberOfTimes: 3)

This may help, good luck!

carriebarnett
carriebarnett
16,732 Points
carriebarnett
carriebarnett
16,732 Points

After researching a bit, I found a link that had a code example that is very close to what we are working on here in the code challenge and it helped me figure it out. http://austinzheng.com/2015/09/29/swift-generics-pt-2/

Look under the Subtile "Generic Functions" and there is a code example.

// Given an item, return an array with that item repeated n times func duplicate<T>(item: T, numberOfTimes n: Int) -> [T] { var buffer : [T] = [] for _ in 0 ..< n { buffer.append(item) } return buffer }

Yuqing Lu
Yuqing Lu
7,032 Points
Yuqing Lu
Yuqing Lu
7,032 Points

func duplicate<T>(item: T, numberOfTimes: Int) -> [T] { return [T](repeating: item, count: numberOfTimes) }

it works for me.

Clinton Johnson
Clinton Johnson
28,714 Points
Clinton Johnson
Clinton Johnson
28,714 Points

Aananya Vyas yea i agree with you and the example above just made it more confusing, Can someone explain it for us.

Daryl Shy
Daryl Shy
11,720 Points
Daryl Shy
Daryl Shy
11,720 Points 
func duplicate<T>(item: T, numberOfTimes: Int) -> [T] {
    var arr: [T] = []
    for _ in 0..<numberOfTimes {
        arr.append(item)
    }
    return arr
}
jc laurent
jc laurent
6,351 Points
jc laurent
jc laurent
6,351 Points

As a returning function you need to use the return key in your function it should looks like

func (a)->arr {

var i = 0 return(i) }