If you want to set some part of the UITextview to BOLD then you can implement the following code :-

    NSString *str = @"I belong to Dehradun";    //  default string
    
    NSMutableAttributedString *attString=[[NSMutableAttributedString alloc] initWithString:str];
 
    UIFont *font_regular = [UIFont fontWithName:@"Helvetica" size:20.0f];   // give the font type
    
    UIFont *font_bold = [UIFont fontWithName:@"Helvetica-Bold" size:20.0f];
    
    [attString addAttribute:NSFontAttributeName value:font_regular range:NSMakeRange(0, 11)];   // set range and font type value
   
    [attString addAttribute:NSFontAttributeName value:font_bold range:NSMakeRange(12, nameString.length - 12)];
    
    [self.txtView setAttributedText:attString];  // set the text to the IBOutlet of UITextview

In this code, I have taken a default string , set the font type (BOLD) , given the range and then set the attributed text to the UITextview.

Similarly, we can do this for UILabel.