Adding different color while editting text in UITextView irrespective of cursor position in Swift

Question

I have a textview where I pre populate it with some required comments for eg: "Hi this is John" would show up in textview with blue color. Now what I need is, whatever new editing is done in textview it would come up in black. So, if I edit the text to "Hi this is Steve". Only "Steve" should be in black and rest should be in blue. I know I will have to use NSAttributedString, but how do I go about it?

Right now I do this on my view load

descriptionTextView.text = myString
descriptionTextView.textColor = UIColor.blue

And this on texteditting

func textViewDidBeginEditing(_ textView: UITextView) {
    descriptionTextView.textColor = UIColor.black
}

But this will change everything to black. Any ideas?

Answer 1

You can achieve this by using UITextViewDelegate

Set delegate for UITextView and make a global variable of NSRange as:

IBOutlet UITextView *textVw;
NSRange textRange;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    UIColor *color = [UIColor blueColor]; // set initial needed color
    NSString *string = @"Hi this is John"; // set initial string to color
    NSDictionary *attrs = @{ NSForegroundColorAttributeName : color };
    NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:string attributes:attrs];
    textVw.attributedText = attrStr;

    //Set delegate of UITextView
    [textVw setDelegate:self];
}

#pragma UITextViewDelegate Methods.
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
     //Check string is written or backspace (with prediction on).
     if (text.length > 1) {

         //Make Range for black text in textview.
         textRange = NSMakeRange(range.location, text.length + 1);

         return YES;
     }

     //Check string is written or backspace.
     if (text.length > 0 && ![text isEqualToString:@" "]) {

         //Make Range for black text in textview.
         textRange = NSMakeRange(range.location, 1);

        return YES;
     }

    return YES;
}

-(void)textViewDidChange:(UITextView *)textView {

    //Check there are some value is written or not.
    if (textRange.length > 0) {

        //Check textview is rest with initial value or not.
        if ([textVw.text caseInsensitiveCompare:@"Hi this is John"] == NSOrderedSame) {

            //Rest value so make string as blue.
            UIColor *color = [UIColor blueColor]; // set initial needed color
            NSString *string = @"Hi this is John"; // set initial string to color
            NSDictionary *attrs = @{ NSForegroundColorAttributeName : color };
            NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:string attributes:attrs];
            textVw.attributedText = attrStr;

        } else {

            NSMutableAttributedString *text =
            [[NSMutableAttributedString alloc]
             initWithAttributedString: textVw.attributedText];

            [text addAttribute:NSForegroundColorAttributeName
                         value:[UIColor blackColor]
                         range:textRange];

            //Add new Attributed value to textView with black color.
            [textVw setAttributedText: text];

        }

        //After assign value to textfiled make textRange varibale as default value for safe handler.
        textRange = NSMakeRange(0, 0);
    }
}

- (void)textViewDidChangeSelection:(UITextView *)textView
{
      //Check there are some value is written or not.

      if (textRange.length > 1) {
             //For maintain cursor position with prediction on.
             [textView setSelectedRange:NSMakeRange(textRange.location + textRange.length , 0)];

      } else if (textRange.length > 0) {
            //For maintain cursor position.
            [textView setSelectedRange:NSMakeRange(textRange.location + 1, 0)];
      }
}