在NSString中帶星號的子串

Question

嗨朋友我想在表格視圖單元格中顯示信用卡號碼，所以我只想顯示最後四個字符，如XXXXXXXXXX1111第一個字符被替換爲x或其他字符我該怎麼做任何一個可以幫助我
我試圖像波紋管

NSString *CardNumber = [CardNumberValues objectAtIndex:indexPath.row]; 
NSRange subStringRange = NSMakeRange(0,[CardNumber length]-4); 
NSMutableCharacterSet *NumSet = [NSMutableCharacterSet characterSetWithRange:subStringRange]; 
CardNumber = [[CardNumber componentsSeparatedByCharactersInSet:NumSet] componentsJoinedByString:@"X"]; 
cell.CardNumber.text = CardNumber; 

，但它不工作u能提出任何參考或代碼...

Answer 1

使用此

NSString *CardNumber = @"123456789"; 
NSString *str_padding=@""; 
    NSRange subStringRange = NSMakeRange(0,[CardNumber length]-4); 
    str_padding =[str_padding stringByPaddingToLength:subStringRange.length withString:@"X" startingAtIndex:0]; 
    CardNumber = [CardNumber stringByReplacingOccurrencesOfString:[NSString stringWithFormat:@"%@",[CardNumber substringToIndex:subStringRange.length]] withString:str_padding]; 
    NSLog(@"%@",CardNumber); 

Answer 2

NSString *cardNumber = [NSString stringWithFormat: @"XXXX-XXXX-XXXX-%@", [[CardNumberValues objectAtIndex:indexPath.row] subStringWithIndex:12]]; 
cell.CardNumber.text = cardNumber; 

我假設卡號是16位數字。