NSAttributedString change color at end of string - ios

Question

This must be an easy thing to do, but I cannot figure it out.
I have a NSMutableAttributedString that has, for example, "This is a test" in it. I want to color the word "test" blue, which I do with this:
NSMutableAttributedString *coloredText = [[NSMutableAttributedString alloc] initWithString:#"This is a test"];
[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(10,4)];
That works just fine. But now I want to set the text color back to black for anything typed after "test".
If I do:
[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(coloredText.string.length, 1)];
I get an objectAtIndex:effectiveRange: out of bounds error. Assumedly because the range extends beyond the length of the string.
If I do:
[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(coloredText.string.length, 0)];
The error goes away but typing after the word "test" remains blue.
How do I set the current color at the insertion point when it is at the end of the string??
Cheers for any input.

Answer 1

In case someone else stumbles upon this, I wanted to post the code I used to solve the problem. I ended up using Kamil's suggestion and adding:
NSAttributedString *selectedString = [textView.attributedText attributedSubstringFromRange:NSMakeRange(textView.attributedText.string.length - 1, 1)];
__block BOOL isBlue = NO;
[selectedString enumerateAttributesInRange:NSMakeRange(0, [selectedString length]) options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:^(NSDictionary *attributes, NSRange range, BOOL *stop) {
isBlue = [[attributes objectForKey:NSForegroundColorAttributeName] isEqual:[UIColor blueColor]];
}];
if (isBlue) {
NSMutableAttributedString *coloredText = [[NSMutableAttributedString alloc] initWithAttributedString:textView.attributedText];
[coloredText addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(textView.attributedText.string.length - 1, 1)];
textView.attributedText = coloredText;
}
to the text changed handler.

Answer 2

You need to recalculate the attributes if the text changes, because their effective range doesn't automatically change with the length of text.