NSMutableAttributedString Append in UITextView - objective-c

Question

I need to append 2 NSMutableAttributedString for my UITextview when user selection different words like the example.
string = #"blabla1 blabla2 blabla3"
in first time the user select #"blabla1"
and the text looks like that #"blabla1 blabla2 blabla3"
and after I select #"blabla3" the result I want to get in My UITextview is #"blabla1 blabla2 blabla3"
now the result I get is #"blabla1 blabla2 blabla3 blabla1 blabla2 blabla3"
that my code :
-(NSMutableAttributedString*)getNSMutableAttributedString:(NSString*)string withRange:(NSRange)range withTextView:(UITextView*)textView
{
if (!str)
{
str = [[NSMutableAttributedString alloc] initWithString:string];
UIFont *font = [UIFont boldSystemFontOfSize:16];
[str addAttribute:NSFontAttributeName value:font range:NSMakeRange(range.location, range.length)];
}
else
{
NSMutableAttributedString *mutableAttString = [[NSMutableAttributedString alloc] initWithString:string];
UIFont *font = [UIFont boldSystemFontOfSize:16];
[mutableAttString addAttribute:NSFontAttributeName value:font range:NSMakeRange(range.location, range.length)];
NSMutableAttributedString *first = str;
NSMutableAttributedString *second = mutableAttString;
NSMutableAttributedString* result = [first mutableCopy];
[result appendAttributedString:second];
str = result;
}
return str;
}

Answer 1

Attributes can be added multiply times to one string.And you create a new attributedString from string, which don't have attributes.
In result you receive #"blabla1 blabla2 blabla3 blabla1 blabla2 blabla3"
-(NSMutableAttributedString*)getNSMutableAttributedString:(NSMutableAttributedString*)string withRange:(NSRange)range withTextView:(UITextView*)textView
{
if (!str)
{
str = [[NSMutableAttributedString alloc] initWithAttributedString:string];
UIFont *font = [UIFont boldSystemFontOfSize:16];
[str addAttribute:NSFontAttributeName value:font range:NSMakeRange(range.location, range.length)];
}
else
{
UIFont *font = [UIFont boldSystemFontOfSize:16];
[str addAttribute:NSFontAttributeName value:font range:NSMakeRange(range.location, range.length)];
}
return str;
}

Answer 2

What you should be doing is get str (the existing attributedText from the UITextView) and then add an attribute to the specific range
str = [textView attributedText];
UIFont *font = [UIFont boldSystemFontOfSize:16];
[str addAttribute:NSFontAttributeName value:font range:NSMakeRange(range.location, range.length)];
return str;
What you are doing is creating a new attributed string with the same content but different attributes and then appending to the existing attributedText. That is why you see the text repeated twice.