How to change colour of all numbers in a string in swift

Question

I am trying to change colour for all numbers present in a string in swift code.Example:

var mystring = \"abc 3423 opqrs 474598 lmno 343543\"


        

Answer 1

First, we need to find the ranges of number existed in the string. One way is to use regular expression

func findNumberRanges(string: String) -> [NSRange]{
    let nsString = string as NSString
    let regex = try? NSRegularExpression(pattern: "[0-9]+", options: [])
    let matches = regex?.matches(in: string, options: .withoutAnchoringBounds, range: NSMakeRange(0, nsString.length))
    return matches?.map{$0.range} ?? []
}

Then we can iterate through ranges of number to add the attribute, in this case to set red color.

func attributedNumberString(string: String, numberAttribute: [String: Any]) -> NSAttributedString{
    let ranges = findNumberRanges(string: string)

    let attributedString = NSMutableAttributedString(string: string)
    for range in ranges{
        attributedString.addAttributes(numberAttribute, range: range)
    }
    return attributedString
}

Here is how it is used:

let redColorAttribute = [ NSForegroundColorAttributeName: UIColor.red]
attributedNumberString(string: "6h40m", numberAttribute: redColorAttribute)

Answer 2

I did something like this for a project, So basically this check whether it's a number and save it's location then by using NSAttributedString, we can easily change the character color like this :-

class ViewController: UIViewController {

@IBOutlet weak var mylabel: UILabel!
let numbers = ["0","1","2","3","4","5","6","7","8","9"]
var mystring = "abc 3423 opqrs 474598 lmno 343543"

override func viewDidLoad() {
    super.viewDidLoad()
    let myAttributedString = NSMutableAttributedString(string: "\(self.mystring)")
    var locations: [Int] = []
    let characters = mystring.characters
    var i = 0
    for letter in characters {
        i = i + 1
        letter.debugDescription
        if numbers.contains(String(letter)) {
            locations.append(i)
        }
    }

    for item in locations {
        print(item)
        let myRange = NSRange(location: item - 1, length: 1)
        myAttributedString.addAttribute(NSForegroundColorAttributeName, value: UIColor.redColor(), range: myRange)
    }
    self.mylabel.attributedText = myAttributedString
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

Here is a screenShot

Answer 3

I am not much familiar with swift but i have try to make demo in objective c and it's works fine as your requirement if it can help,

  NSString *str = @"abc 3423 opqrs 474598 lmno 343543";

NSMutableAttributedString *str1 = [[NSMutableAttributedString alloc]initWithString:@"abc 3423 opqrs 474598 lmno 343543"];

NSArray *arr = [str componentsSeparatedByString:@" "];

for (int i = 0; i < arr.count; i++) {


    NSString *temp = [arr objectAtIndex:i];

    NSCharacterSet* notDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
    if ([temp rangeOfCharacterFromSet:notDigits].location == NSNotFound)
    {
        NSDictionary *attrs = @{

                                NSForegroundColorAttributeName:[UIColor redColor]
                                };

        NSRange range = [str rangeOfString:[arr objectAtIndex:i]];

        [str1 addAttributes:attrs range:range];
    }


}

UILabel *temp = [[UILabel alloc]initWithFrame:CGRectMake(20, 20, 300, 50)];

[self.view addSubview:temp];

temp.attributedText = str1;

You can use logic and concept and can use in swift as your requirement.

Hope this will help :)

Answer 4

Here's an extension using Swift 5 using Zig's answer as reference:

  extension String {

    func changeColorForNumbers() -> NSMutableAttributedString {
        let red = [NSAttributedString.Key.foregroundColor: UIColor.red]

        let myAttributedString = NSMutableAttributedString()
        for letter in self.unicodeScalars {
            let myLetter : NSAttributedString
            if CharacterSet.decimalDigits.contains(letter) {
                myLetter = NSAttributedString(string: "\(letter)", attributes: orange)
            } else {
                myLetter = NSAttributedString(string: "\(letter)")
            }
            myAttributedString.append(myLetter)
        }

        return myAttributedString
    }

}

Answer 5

I think there's a more efficient way to do this. Instead of finding the locations of the numbers and then creating a range for each of them, just change it on the fly.

    let myString = "abc 3423 opqrs 474598 lmno 343543"
    let redFont = [NSForegroundColorAttributeName: UIColor.red]

    let myAttributedString = NSMutableAttributedString()
    for letter in myString.unicodeScalars {
        let myLetter : NSAttributedString
        if CharacterSet.decimalDigits.contains(letter) {
            myLetter = NSAttributedString(string: "\(letter)", attributes: redFont)
        } else {
            myLetter = NSAttributedString(string: "\(letter)")
        }
        myAttributedString.append(myLetter)
    }

    myLabel.attributedText = myAttributedString

In addition to being more efficient, checking membership in the CharacterSet.decimalDigits is localization-friendly if you intend to support that.

Answer 6

NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:"Your Text"];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0,5)]; //give range where you want
[string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColor] range:NSMakeRange(5,6)];//give range where you want
[string addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(11,5)]; //give range where you want
YourLable.attributedText = string;