How to convert a String (numeric) in a Int array in Swift

Question

I'd like to know how can I convert a String in an Int array in Swift. In Java I've always done it like this:

String myString = "123456789";
int[] myArray = new int[myString.lenght()];
for(int i=0;i<myArray.lenght;i++){
   myArray[i] = Integer.parseInt(myString.charAt(i));
}  

Thanks everyone for helping!

Solution 1

let str = "123456789"
let intArray = map(str) { String($0).toInt() ?? 0 }

• map() iterates Characters in str
• String($0) converts Character to String
• .toInt() converts String to Int. If failed(??), use 0.

If you prefer for loop, try:

let str = "123456789"
var intArray: [Int] = []

for chr in str {
    intArray.append(String(chr).toInt() ?? 0)
}

OR, if you want to iterate indices of the String:

let str = "123456789"
var intArray: [Int] = []

for i in indices(str) {
    intArray.append(String(str[i]).toInt() ?? 0)
}

Solution 2

You can use flatMap to convert the characters into a string and coerce the character strings into an integer:

Swift 2 or 3

let string = "123456789"
let digits = string.characters.flatMap{Int(String($0))}
print(digits)   // [1, 2, 3, 4, 5, 6, 7, 8, 9]"

Swift 4

let string = "123456789"
let digits = string.flatMap{Int(String($0))}
print(digits)   // [1, 2, 3, 4, 5, 6, 7, 8, 9]"

Swift 4.1

let digits = string.compactMap{Int(String($0))}

Swift 5 or later

We can use the new Character Property wholeNumberValue https://developer.apple.com/documentation/swift/character/3127025-wholenumbervalue

let digits = string.compactMap{$0.wholeNumberValue}

Solution 3

Swift 3

Int array to String

let arjun = [1,32,45,5]
    print(self.get_numbers(array: arjun))

 func get_numbers(array:[Int]) -> String {
        let stringArray = array.flatMap { String(describing: $0) }
        return stringArray.joined(separator: ",")

String to Int Array

let arjun = "1,32,45,5"
    print(self.get_numbers(stringtext: arjun))

    func get_numbers(stringtext:String) -> [Int] {
    let StringRecordedArr = stringtext.components(separatedBy: ",")
    return StringRecordedArr.map { Int($0)!}   
}

Solution 4

@rintaro's answer is correct, but I just wanted to add that you can use reduce to weed out any characters that can't be converted to an Int, and even display a warning message if that happens:

let str = "123456789"
let intArray = reduce(str, [Int]()) { (var array: [Int], char: Character) -> [Int] in
    if let i = String(char).toInt() {
        array.append(i)
    } else {
        println("Warning: could not convert character \(char) to an integer")
    }
    return array
}

The advantages are:

• if intArray contains zeros you will know that there was a 0 in str, and not some other character that turned into a zero
• you will get told if there is a non-Int character that is possibly screwing things up.

View more solutions

Comments

[Nate Cook]

You have a loop in your loop—calling advance over and over like that is a bad idea, since you're making the program step through the string from the beginning each time.

[Luca Angeletti]

toInt() is no longer available in String in Swift 2.x.

[leanne]

Swift 4.1 deprecates .flatMap for this use case. Use .compactMap instead: let digits = string.compactMap{Int(String($0))}

[leanne]

Swift 4.1 deprecates .flatMap for this use case. Instead, use .compactMap: let intArray = string.components(separatedBy: "").compactMap { Int($0) }

[Leo Dabus]

@leanne this is wrong it would result in an array with a single element of the same value of the input [123456789]. The first method components(separatedBy: "") would result in a single string element ["123456789"]

[leanne]

I simply replaced the deprecated .flatMap with the new .compactMap, @LeoDabus. Both results are the same. As printed in Xcode's debug console: [123456789] and [123456789]. Note that I am not judging whether the result is appropriate for the original question, but simply remarking for anyone who comes here that .flatMap has been deprecated in favor of .compactMap in cases where one is attempting to achieve a result that removes nil values.

[Mark Rotteveel]

Please don't post only code as answer, but also provide an explanation what your code does and how it solves the problem of the question. Answers with an explanation are usually more helpful and of better quality, and are more likely to attract upvotes.