最近做的專案有關於銀行卡號輸入的情景設定，參照微信綁卡操作，輸入卡號數字每隔4位空1位。

由於趕進度，沒細作研究，特此網上摘錄的程式碼片段，如下：

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    
    if (textField == self.text_cardno) {
        NSString *text = [self.text_cardno text];
        
        NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789\b"];
        string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];
        if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {
            return NO;
        }
        
        text = [text stringByReplacingCharactersInRange:range withString:string];
        text = [text stringByReplacingOccurrencesOfString:@" " withString:@""];
        
        NSString *newString = @"";
        while (text.length > 0) {
            NSString *subString = [text substringToIndex:MIN(text.length, 4)];
            newString = [newString stringByAppendingString:subString];
            if (subString.length == 4) {
                newString = [newString stringByAppendingString:@" "];
            }
            text = [text substringFromIndex:MIN(text.length, 4)];
        }
        
        newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];
        
        // 限制長度
        if (newString.length >= 24) {
            return NO;
        }
        
        [self.text_cardno setText:newString];
        
        return NO;
        
    }
    return YES;
}
 

// 銀行卡號轉正常號 － 去除4位間的空格
-(NSString *)bankNumToNormalNum
{
    return [self.text_cardno.text stringByReplacingOccurrencesOfString:@" " withString:@""];
}