Populating Array in Swift 4 with for-loop without using the index

Question

I need to populate an Array (already declared and initialized) using a for loop in order to create a determinate amount of items.

I ended up with the following code:

    func createValues() -> Array<Int> {

        let usableRange:Range = 6..<11;

        var arrayOfValues: Array<Int>=[]; //Array declared and initialized

        for i in 0..<10 {

            arrayOfValues.append(random(usableRange));

            print(arrayOfValues[i]);

        }

        return arrayOfValues;
    }

this code does what I expect it to do just fine. However, as soon as I comment out the line

 print(arrayOfValues[i]);

Xcode throws the following warning:

Immutable value 'i' was never used; consider replacing with '_' or removing it

If I accept the suggestion the code works, but not as fine as it did before.

I'm just transitioning from Obj-C to Swift and I don't really know what the proper way to do this should be. Any help would be appreciated. Thanks in advance.

P.S. I'm aware that I don't need semicolons anymore, but old habits die hard, I guess...

"not as fine as it did before." Why not? The only difference is that it doesn't print anything — Leo Dabus
– Leo Dabus, Commented Apr 29, 2018 at 11:49
Please learn to read and understand error / warning messages. This is one of the most comprehensible. — vadian
– vadian, Commented Apr 29, 2018 at 11:52
well, by the press of a button, the code should generate random numbers between a range. If the average of the given numbers is not the average of the range it generates new numbers until it does. This is all fine, but when I replace the 'i' for a _, I have to press the button many times until I have something printed on the console. I'm debugging it right now to see where the problem can be... — Marcal
– Marcal, Commented Apr 29, 2018 at 11:53
@vadian I understand the warning just fine. The question is how to do what I want to do in a proper warning-free way — Marcal
– Marcal, Commented Apr 29, 2018 at 11:55
As Leo already mentioned the code does exactly the same (creating 10 random numbers) except it does not print anything in the loop. — vadian
– vadian, Commented Apr 29, 2018 at 11:56

gnasher729 · Accepted Answer · 2018-04-29 14:27:51Z

1

Since you don't use i, you can just write

for _ in 0 ..< 10

The _ means "yes, there is a value, but I don't care about it", here and in many other situations.

answered Apr 29, 2018 at 14:27

gnasher729

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Seyed Samad Gholamzadeh · Accepted Answer · 2018-04-29 13:30:20Z

0

If you want just a good alternative for your code, I'm offering you this:

var i: Int = 0

while i < 10 {

  arrayOfValues.append(random(usableRange))
  i += 1

}

answered Apr 29, 2018 at 13:30

Seyed Samad Gholamzadeh

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matt · Accepted Answer · 2018-04-29 14:57:55Z

0

If the goal is to generate an array of random numbers in your given range, I would suggest you simply generate it directly. There is no need for the for loop.

let usableRange = UInt32(6)..<UInt32(11)
let arr = (0..<10).map { _ in Int(
    arc4random_uniform(usableRange.upperBound - usableRange.lowerBound) 
    + usableRange.lowerBound
)}

answered Apr 29, 2018 at 14:57

matt

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Philip Niedertscheider · Accepted Answer · 2018-04-29 15:12:29Z

0

Array has a designated initalizer, which initalizes an array with a given size and a repeated value:

let values = Array(repeating: "VALUE", count: 5)
print(fiveZs)
// Prints "["VALUE", "VALUE", "VALUE", "VALUE", "VALUE"]"

Source: Apple Documentation

answered Apr 29, 2018 at 15:12

Philip Niedertscheider

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