Hey got some links for you ,might be helpful for you. Also got answer to strike-through for iOS version below 6.
I got below code working for iOS 6 and above
NSMutableAttributedString *attString=[[NSMutableAttributedString alloc]initWithString:@"PROVIDE_YOUR_STRING"];
[attString addAttribute:NSStrikethroughStyleAttributeName value:[NSNumber numberWithInt:2] range:NSMakeRange(0,[attString length])];
_label.attributedText = attString;