uitextfield输入字符限制

-(UITextField*)createField:(NSString*)placeholder andTag:(int)tag andFont:(double)font{

    UITextField * field =[[UITextField alloc]init];

    field.frame = CGRectMake(, , Main_Width-, );

    field.delegate = self;

    field.userInteractionEnabled = YES;

    field.textAlignment = NSTextAlignmentLeft;

    field.keyboardType = UIKeyboardTypeDefault;

//    field.returnKeyType = UIReturnKeySend;

    field.tag = tag;

    field.placeholder =placeholder;

//    field.text = placeholder;

    field.textColor = littleBlackColor;

    [field setFont:[UIFont fontWithName:@"STHeitiSC" size:font]];

    [field addTarget:self action:@selector(textFieldWithText:) forControlEvents:UIControlEventEditingChanged];

    return field;

}

-(void)textFieldWithText:(UITextField *)textField{

    UITextField * field = (UITextField*)textField;

    switch (textField.tag) {

        case ://发车单位/收车单位

            if ([self textField:field shouldChangeCharactersInRange:NSMakeRange(, ) replacementString:@""]) {

                [dic setObject:field.text forKey:@"unitname"]; //送达单位、收车单位

            }

            break;

        case : //联系人

            if ([self textField:field shouldChangeCharactersInRange:NSMakeRange(, ) replacementString:@""]) {

                [dic setObject:field.text forKey:@"contact"];

            }

            break;

        case ://联系电话

            if ([self textField:field shouldChangeCharactersInRange:NSMakeRange(, ) replacementString:@""]) {

                [dic setObject:field.text forKey:@"phone"];

            }

            break;

        case ://详细地址

            if ([self textField:field shouldChangeCharactersInRange:NSMakeRange(, ) replacementString:@""]) {

                [dic setObject:field.text forKey:@"address"];

            }

            break;

        default:

            break;

    }

}

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;

{

//string就是此时输入的那个字符textField就是此时正在输入的那个输入框返回YES就是可以改变输入框的值NO相反

    if ([string isEqualToString:@"\n"])  //按会车可以改变

    {

        return YES;

    }

    NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string]; //得到输入框的内容

    switch (textField.tag) {

        case ://发车单位/收车单位

            if ([toBeString length] > ) {

                textField.text = [toBeString substringToIndex:];

                [self createUIAlertController:@"单位输入不能超过20个字符"];

                return NO;

            }

            break;

        case : //联系人

            if ([toBeString length] > ) {

                textField.text = [toBeString substringToIndex:];

                [self createUIAlertController:@"联系人输入不能超过10个字符"];

                return NO;

            }

            break;

        case ://联系电话

            if ([toBeString length] > ) {

                textField.text = [toBeString substringToIndex:];

                [self createUIAlertController:@"联系电话输入不能超过11个字符"];

                return NO;

            }

            break;

        case ://详细地址

            if ([toBeString length] > ) {

                textField.text = [toBeString substringToIndex:];

                [self createUIAlertController:@"详细地址输入不能超过30个字符"];

                return NO;

            }

            break;

        default:

            break;

    }

    return YES;

}