How to change color of text strings inside UITextView in Swift3

Question

I have looked at some existing questions posts here and I tried to implement all code but ended up not being able to successfully implement any code. Actually, I think I com

Answer 1

In this I have taken string "world" as example. When you r typing in textview then This method is in working

func textViewDidChange(_ textView: UITextView) {
        let attrStr = NSMutableAttributedString(string:txtview.text)
        let inputLength = attrStr.string.characters.count
        let searchString = "world"
        let searchLength = searchString.characters.count
        var range = NSRange(location: 0, length: attrStr.length)

        while (range.location != NSNotFound) {
            range = (attrStr.string as NSString).range(of: searchString, options: [], range: range)
            if (range.location != NSNotFound) {
                attrStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.red, range: NSRange(location: range.location, length: searchLength))
                range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
                textView.attributedText = attrStr
            }
        }    
}

But when You have already set initial text of textview then use this method

func textViewDidBeginEditing(_ textView: UITextView) {
        //Just set your text as you set in textview
        let attrStr = NSMutableAttributedString(string: "hello world I ma jeckjklwefljlwjflkjwfkljelwfjklfgjwklfjlkwgjwlgkjwklsgjklsjgklsdjgkljdslkgjsdlkgjlksdjgldjsgldjskl world nsfhjklshfklhsllsd fgiw world")
        let inputLength = attrStr.string.characters.count
        let searchString = "world"
        let searchLength = searchString.characters.count
        var range = NSRange(location: 0, length: attrStr.length)

        while (range.location != NSNotFound) {
            range = (attrStr.string as NSString).range(of: searchString, options: [], range: range)
            if (range.location != NSNotFound) {
                attrStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.red, range: NSRange(location: range.location, length: searchLength))
                range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
                textView.attributedText = attrStr
            }
          }  
  }

For Multiple Strings, You can do like this SWIFT 3

func textViewDidChange(_ textView: UITextView) {
        let attrStr = NSMutableAttributedString(string: txtview.text)
        let inputLength = attrStr.string.characters.count
        let searchString : NSArray = NSArray.init(objects: "hello","world")
        for i in 0...searchString.count-1
        {

             let string : String = searchString.object(at: i) as! String
             let searchLength = string.characters.count
             var range = NSRange(location: 0, length: attrStr.length)

             while (range.location != NSNotFound) {
                 range = (attrStr.string as NSString).range(of: string, options: [], range: range)
                 if (range.location != NSNotFound) {
                 attrStr.addAttribute(NSForegroundColorAttributeName, value: UIColor.red, range: NSRange(location: range.location, length: searchLength))
                 range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
                 textView.attributedText = attrStr
        }
    }   
  }
}

OBJECTIVE C
For Multiple Strings, You can do like this

-(void)textViewDidChange:(UITextView *)textView
{
    NSMutableAttributedString *attstr = [[NSMutableAttributedString alloc]initWithString:textView.text];
    NSUInteger characterCount = [attstr length];
    NSArray *arr = [[NSArray alloc]initWithObjects:@"football",@"player",nil];

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

    NSUInteger searchlength = [[NSString stringWithFormat:@"%@",[arr objectAtIndex:i]] length];
    NSRange range1 = NSMakeRange(0, attstr.length);

    while (range1.location != NSNotFound) {
        range1 =[attstr.string rangeOfString:[NSString stringWithFormat:@"%@",[arr objectAtIndex:i]] options:0 range:range1];
        if (range1.location !=NSNotFound) {
            [attstr addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(range1.location, searchlength)];
            [attstr addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:20.0]  range:range1];
            range1 = NSMakeRange(range1.location + range1.length, characterCount -(range1.location + range1.length));
            textView.attributedText = attstr;
        }
    }
}