self.inputTextField.delegate=self;

//調取數字鍵盤

self.inputTextField.keyboardType = UIKeyboardTypeNumberPad;

在textfield的delegate方法中：

#pragma mark ------TextFieldDelegate----------

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
//    NSLog(@"string=%@",string);
//    NSLog(@"range location=%ld,length=%ld",range.location,range.length);
   
    NSString *BeString;
    
    if ([string isEqualToString:@""]) { //刪除資料
        BOOL isKong=NO;//是否要刪除的是空格
        NSString *ss=[textField.text substringWithRange:NSMakeRange(range.location, 1)];
        if ([ss isEqualToString:@" "]) { //刪除空格
            
            isKong=YES;
            
            if (range.location==0) {//第一個字母是空格
                NSLog(@"textfied==%@",textField.text);
                return YES;
            }
            textField.text=[textField.text stringByReplacingCharactersInRange:NSMakeRange(range.location-1, 1) withString:@" "];
            BeString=textField.text;
        }else{
            BeString=[textField.text stringByReplacingCharactersInRange:NSMakeRange(range.location, 1) withString:@" "];
        }
        //對被刪除之後的資料去空格，重新加空格，末尾不要空格
        textField.text=[self getSpace4StringWith:BeString lastHaveSpace:NO];
        
        if (range.location>[textField.text length]) {
            textField.text=[textField.text stringByAppendingString:@" "];
        }else{
            textField.text=[NSString stringWithFormat:@"%@ %@",[textField.text substringToIndex:range.location],[textField.text substringFromIndex:range.location] ];
            if (isKong) {
                [textField setSelectedRange:NSMakeRange(range.location, 1)];
            }else{
                [textField setSelectedRange:NSMakeRange(range.location, 1)];
            }
        }
        NSLog(@"Bestring=%@",BeString);
        return YES;
    }else{
        BeString=[textField.text stringByReplacingCharactersInRange:range withString:@"s"];
    }
    if (BeString.length>23) { //只能輸入19位
        textField.text = [textField.text substringToIndex:23];
        return NO;
    }

//    NSLog(@"beString=%@",BeString);
    textField.text=[self getSpace4StringWith:BeString lastHaveSpace:YES];
    NSLog(@"tt=%@",textField.text);
    //得到字元“s”的位置，將它定為游標的位置
    NSRange sRange=[textField.text rangeOfString:@"s"];
    
    textField.selectedRange=sRange;
    return YES;
}
//得到4個字元之間以空格相間隔的字串,最後一串若是4個字元，那麼最後一位要不要空格，要則hasSpace=YES,不要則hasSpace=NO
-(NSString *)getSpace4StringWith:(NSString *)str lastHaveSpace:(BOOL)hasSpace
{
   NSString *BeString=[str stringByReplacingOccurrencesOfString:@" " withString:@""];
    
    NSString *
 
[email protected]"";
    while (BeString.length>4) {
        NSString *little=[BeString substringToIndex:4];
        finalStr=[finalStr stringByAppendingFormat:@"%@ ",little];
        BeString=[BeString substringFromIndex:4];
    }
    finalStr=[finalStr stringByAppendingString:BeString];
    if (hasSpace) {
        if (BeString.length==4) {
            finalStr=[NSString stringWithFormat:@"%@ ",finalStr];
        }
    }
    return finalStr;
}