Changing specific text's color using NSMutableAttributedString in Swift

The issue I am having is that I want to be able to change the textColor of certain text in a TextView. I am using a concatenated string, and just want the strings I am appending into the TextView's text. It appears that what I want to use is NSMutableAttributedString, but I am not finding any resources of how to use this in Swift. What I have so far is something like this:

let string = "A \(stringOne) with \(stringTwo)"
var attributedString = NSMutableAttributedString(string: string)
textView.attributedText = attributedString

From here I know I need to find the range of words that need to have their textColor changed and then add them to the attributed string. What I need to know is how to find the correct strings from the attributedString, and then change their textColor.

Since I have too low of a rating I can't answer my own question, but here is the answer I found

I found my own answer by translating from translating some code from

Change attributes of substrings in a NSAttributedString

Here is the example of implementation in Swift:

let string = "A \(stringOne) and \(stringTwo)"
var attributedString = NSMutableAttributedString(string:string)

let stringOneRegex = NSRegularExpression(pattern: nameString, options: nil, error: nil)
let stringOneMatches = stringOneRegex.matchesInString(longString, options: nil, range: NSMakeRange(0, attributedString.length))
for stringOneMatch in stringOneMatches {
    let wordRange = stringOneMatch.rangeAtIndex(0)
    attributedString.addAttribute(NSForegroundColorAttributeName, value: UIColor.nameColor(), range: wordRange)
}

textView.attributedText = attributedString

Since I am wanting to change the textColor of multiple Strings I will make a helper function to handle this, but this works for changing the textColor.

let mainString = "Hello World"
let stringToColor = "World"

SWIFT 5

let range = (mainString as NSString).range(of: stringToColor)

let mutableAttributedString = NSMutableAttributedString.init(string: mainString)
mutableAttributedString.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.red, range: range)

textField = UITextField.init(frame: CGRect(x:10, y:20, width:100, height: 100))
textField.attributedText = mutableAttributedString

SWIFT 4.2

let range = (mainString as NSString).range(of: stringToColor)
    

let mutableAttributedString = NSMutableAttributedString.init(string: mainString)
mutableAttributedString.addAttribute(NSAttributedStringKey.foregroundColor, value: UIColor.red, range: range)     
    
textField = UITextField.init(frame: CGRect(x:10, y:20, width:100, height: 100))
textField.attributedText = mutableAttributedString

I see you have answered the question somewhat, but to provide a slightly more concise way without using regex to answer to the title question:

To change the colour of a length of text you need to know the start and end index of the coloured-to-be characters in the string e.g.

var main_string = "Hello World"
var string_to_color = "World"

var range = (main_string as NSString).rangeOfString(string_to_color)

Then you convert to attributed string and use 'add attribute' with NSForegroundColorAttributeName:

var attributedString = NSMutableAttributedString(string:main_string)
attributedString.addAttribute(NSForegroundColorAttributeName, value: UIColor.redColor() , range: range)

A list of further standard attributes you can set can be found in Apple's documentation

Swift 2.1 Update:

 let text = "We tried to make this app as most intuitive as possible for you. If you have any questions don't hesitate to ask us. For a detailed manual just click here."
 let linkTextWithColor = "click here"

 let range = (text as NSString).rangeOfString(linkTextWithColor)

 let attributedString = NSMutableAttributedString(string:text)
 attributedString.addAttribute(NSForegroundColorAttributeName, value: UIColor.redColor() , range: range)

 self.helpText.attributedText = attributedString

self.helpText is a UILabel outlet.