properties cannot be accessed in error handler

Question

Two questions:

Looking at the highlighted line in https://github.com/bwu-dart/bwu_datagrid/blob/master/example/src/composite_editor_item_details/app_element.dart#L120

1) why does the line

var idx = e.validationResults.errors.length;

always throws an error?

Exception: Uncaught Error: The null object does not have a getter 'length'.

NoSuchMethodError: method not found: 'length'
Receiver: null
Arguments: []
Stack Trace:
#0      Object.noSuchMethod (dart:core-patch/object_patch.dart:45)
#1      validationErrorHandler (http://localhost:8080/epimss_design.html.12.dart:184:42)
#2      _RootZone.runUnaryGuarded (dart:async/zone.dart:1020)
#3      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:341)
#4      _BufferingStreamSubscription._add (dart:async/stream_impl.dart:270)
#5      _SyncBroadcastStreamController._sendData (dart:async/broadcast_stream_controller.dart:346)
#6      _BroadcastStreamController.add (dart:async/broadcast_stream_controller.dart:237)
#7      EventBus.fire (package:bwu_datagrid/core/event_bus.dart:61:19)
#8      _commitCurrentEdit (package:bwu_datagrid/bwu_datagrid.dart:3626:25)
#9      EditorLock.commitCurrentEdit (package:bwu_datagrid/core/range.dart:235:82)
#10     BwuDatagrid._commitEditAndSetFocus (package:bwu_datagrid/bwu_datagrid.dart:3045:40)
#11     _handleKeyDown (package:bwu_datagrid/bwu_datagrid.dart:2632:39)

The same thing happens for other properties as well such as field and column etc.

2) How can I test that the validationResult returns true? The error handler seems to only fires when there is an ValidationError.

My validator is shown below

 import 'package:bwu_datagrid/datagrid/helpers.dart' show Column, GridOptions,
    MapDataItem, MapDataItemProvider;
  import 'package:bwu_datagrid/bwu_datagrid.dart' show BwuDatagrid;
  import 'package:bwu_datagrid/formatters/formatters.dart' show CheckmarkFormatter;
  import 'package:bwu_datagrid/editors/editors.dart' show CheckboxEditor, EditorArgs,
    IntegerEditor, TextEditor;
  import 'package:bwu_datagrid/core/core.dart' show AddNewRow, ActiveCellChanged,
    ItemBase, ValidationError;
  import 'package:bwu_datagrid/plugins/row_selection_model.dart' show RowSelectionModel;

  import 'package:epimss_podo/reg.dart' show Email, EMAIL_FORM_EVENT;
  import 'package:epimss_shared/shared.dart' show toggleCoreCollapse, onBwuCellChangeHandler;
  import 'package:epimss_shared/validators.dart' show BwuRequiredEmailValidator,
    BwuRequiredNounValidator;

Custom validators:

const String REQUIRED_EMAIL_REGEX = r"\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b";
const String REQUIRED_NOUN_REGEX = r"\b[a-z'-]{2,}\b";

final RegExp _requiredNounValidator = new RegExp( REQUIRED_NOUN_REGEX, caseSensitive: false );
bool isRequiredNounValid( String property ) =>
    _requiredNounValidator.hasMatch( property );

final RegExp _requiredEmailPropertyValidator = new RegExp( REQUIRED_EMAIL_REGEX, caseSensitive: false );
bool isRequiredEmailPropertyValid( String property ) => _requiredEmailPropertyValidator.hasMatch( property );


class BwuRequiredEmailValidator extends bwu.Validator {
  bwu.ValidationResult call( dynamic value ) {
    if ( isRequiredEmailPropertyValid( value ) ) {
      return new bwu.ValidationResult( true );
    } else {
      return new bwu.ValidationResult( false, 'Valid email address required.' );
    }
  }
}


class BwuRequiredNounValidator extends bwu.Validator {
  bwu.ValidationResult call( dynamic value ) {
    if ( isRequiredNounValid( value) ) {
      return new bwu.ValidationResult( true );
    } else {
      return new bwu.ValidationResult( false, 'Valid noun is required.' );
    }
  }
}

Validation error handler:

void validationErrorHandler( ValidationError e ) {
  //print ( e.validationResults.errors.length );
  print ( e.column.field );

  if ( e.validationResults.isValid )
    print( 'retVal is true' );
  else
    print( 'retVal is false' );

  errorMsg = e.validationResults.message;
  var editor = e.editor;
  print ( 'valResult valid |' + e.validationResults.isValid.toString() );

  var result = e.validationResults;

  if ( e.validationResults.isValid ) {
    errorMsg = 'EMAIL';
  } else {
    errorMsg = result.message;
  }

  print( editor.runtimeType ); // aslways print TextEditor

  if ( editor != null ) {
    //var colId = editor.column.id;
    if ( editor is TypeEditor ) {
      email.isTypeValid = true;
    }

    if ( editor is AddressEditor ) {
      email.isAddressValid = false;
    }

    //print( encode ( email ) );
  }
}

Answer 1

You get the exception because the field e.validationResults.errors is null.
You can't access the length property of null thus the exception is thrown.
The field errors is null because in this call

return new bwu.ValidationResult( false, 'Valid email address required.' );

you didn't pass a value for the optional errors parameter

class ValidationResult {
  bool isValid = false;
  String message;
  List<ValidationErrorSource> errors;

  ValidationResult(this.isValid, [this.message, this.errors]);
}

Hint:

As far as I know breakpoints don't work for code within <script> tags (I saw this in the example code I got in an email).
I therefore advise to move your code from the email_form.html file to a email_form.dart file.
Then you can use the debugger and investigate the values at runtime which also helps a lot to learn what others peoples code is actually doing.

Fire custom event from Editor

class AddressEditor extends bwu.TextEditor {

static const VALIDATION_SUCCEEDED = const EventType<ValidationError>(
      'custom-validation-succeeded');
  ...

@override
bwu.ValidationResult validate() {
  var result = super.validate();

  args.grid.eventBus.fire(AddressEditor.VALIDATION_SUCCEEDED, new ValidationError(this,
    editor: this,
    cellNode: args.grid.getActiveCellNode(),
    validationResults: result,
    cell: args.grid.getActiveCell(),
    column: column));
  return result;
}

// you can register the same handler as for the validation error event grid.eventBus.onEvent(AddressEditor.VALIDATION_SUCCEEDED).listen(validationErrorHandler);

I have not tried this code but it should work.