NoSuchMethodError: Class 'DateTime' has no instance getter 'isNotEmpty'.

[awhitford]

Running into a strange problem... Have a field like:

                    FormBuilderDateTimePicker(
                      attribute: "birthday",
                      inputType: InputType.date,
                      initialDatePickerMode: DatePickerMode.year,
                      initialDate: DateTime.now().subtract(Duration(days:18*365)),
                      lastDate: DateTime.now().subtract(Duration(days:13*365)),
                      decoration: InputDecoration(
                          icon: Icon(Icons.cake),
                          labelText: "Birthday (optional)"),
                      format: DateFormat("MMM dd, yyyy"),
                      validators: [FormBuilderValidators.date()],
                    ),

When this field is empty, there is no form submission problem. However, when a date is specified, then I get an exception:

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: Class 'DateTime' has no instance getter 'isNotEmpty'.
Receiver: Instance of 'DateTime'
Tried calling: isNotEmpty
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1      FormBuilderValidators.date.<anonymous closure> (package:flutter_form_builder/src/form_builder_validators.dart:192:52)
#2      _FormBuilderDateTimePickerState.build.<anonymous closure> (package:flutter_form_builder/src/fields/form_builder_date_time_picker.dart:274:35)
#3      FormFieldState._validate (package:flutter/src/widgets/form.dart)
#4      FormFieldState.validate.<anonymous closure> (package:flutter/src/widgets/form.dart:364:7)
#5      State.setState (package:flutter/src/widgets/framework.dart:1141:30)
#6      FormFieldState.validate (package:flutter/src/widgets/form.dart:363:5)
#7      FormState._validate (package:flutter/src/widgets/form.dart:203:25)
#8      FormState.validate (package:flutter/src/widgets/form.dart:197:12)
#9      F<…>

Please note that I am using version 3.5.4, Flutter 1.9.1+hotfix.2, and the iOS Simulator (Version 11.0).

[awhitford]

It appears to be related to this code:

  /// [FormFieldValidator] that requires the field's value to be a valid date string.
  static FormFieldValidator date({
    String errorText = "This field requires a valid date string.",
  }) {
    return (valueCandidate) {
      if (valueCandidate != null && valueCandidate.isNotEmpty) {
        if (!isDate(valueCandidate)) return errorText;
      }
      return null;
    };
  }

valueCandidate must be a DateTime rather than a String, so the isNotEmpty does not exist.

💡 Note that this may be related to the fact that I am using initialDate and/or lastDate because I do not recall running into this before and the validation code has not changed.

[awhitford]

I confirmed that the issue has nothing to do with using the initialDate or lastDate because if I comment that out, it still trips on this exception. When a date is selected, the value is a DateTime (not a String), so the isNotEmpty method does not exist.

Am I doing something wrong? Or does the date validator logic need to be tweaked?

[awhitford]

🤔 Is the validator completely redundant in this case? Can I trust that the Date Picker will ALWAYS yield a valid Date (or null/blank)? (If so, then I should simply remove the validator.)

[danvick]

Hi @awhitford,
In this case the validator is irrelevant since FormBuilderDateTimePicker always gives a DateTime value.

The validator is supposed to be used to validate that a String conforms to a valid date string.

Maybe we should rename the validator from FormBuilderValidators.date() to FormBuilderValidators.dateString()

[awhitford]

Thank you for confirming.

A rename isn't necessary -- just a comment for the developer is likely enough.