NSMutableString to set some part of sting BOLD -- IOS

 NSString *textStr = @"This is a good boy";

NSRange rangeBold = [textStr rangeOfString:@"good"];

 UIFont *changeFont = [UIFont boldSystemFontOfSize:13];

        

  NSDictionary *dictBoldText = [NSDictionary dictionaryWithObjectsAndKeys: changeFont, NSFontAttributeName, nil];

        

 NSMutableAttributedString *mutAttrTextViewString = [[NSMutableAttributedString alloc] initWithString:textStr];

        

  [mutAttrTextViewString setAttributes:dictBoldText range:rangeBold];

        

       

    YOUR_TEXT_VIEW.attributedText = mutAttrTextViewString;