I want to add mandatory field mark in textfield placeholder text like below image please suggest me i am totally confused how to do it

You can use :
NSMutableAttributedString *attriButedString = [[NSMutableAttributedString alloc]initWithString:@"Mandatory*"];
[attriButedString addAttribute:NSForegroundColorAttributeName
value:[NSColor lightGrayColor]
range:NSMakeRange(0, 9)];
[attriButedString addAttribute:NSForegroundColorAttributeName
value:[NSColor redColor]
range:NSMakeRange(9, 1)];
[[self.textField cell] setPlaceholderAttributedString:attriButedString];
This will look like as:

Note: Instead of hard-coded range you can calculate according to your stringlength.

If you are creating TextField from xib click on text field and go to attribute inspecter and fill your placeholder name in placeholder text feild
Try with this.....
[tfSubject setValue:[UIColor colorWithRed:249.0/255.0 green:204.0/255.0 blue:88.0/255.0 alpha:1.0] forKeyPath:@"_placeholderLabel.textColor"];