CvField add type check methods

[ebtone]

like this

bool isSubtypeOf<SUPERTYPE>() => isTypeASubtypeOfB<T, SUPERTYPE>();

bool isSupertypeOf<SUBTYPE>() => isTypeASubtypeOfB<SUBTYPE, T>();

[alextekartik]

Not sure how to implement that. The runtime info we have does not allow testing whether a type is subtype of another type (unless I'm missing something). We can only check whether a value matches a given type

[ebtone]

Not sure how to implement that. The runtime info we have does not allow testing whether a type is subtype of another type (unless I'm missing something). We can only check whether a value matches a given type

/// Content value column.
abstract class CvColumn<T extends Object?> implements RawColumn, RawTyped {

  ......

  /// Column type is subtype of supertype
  bool isSubtypeOf<SUPERTYPE>();

  /// Column type is supertype of subtype
  bool isSupertypeOf<SUBTYPE>();
}


mixin CvColumnMixin<T> implements CvColumn<T> {

  ......

  @override
  bool isSubtypeOf<SUPERTYPE>() => <T>[] is List<SUPERTYPE>;

  @override
  bool isSupertypeOf<SUBTYPE>() => <SUBTYPE>[] is List<T>;

  ......
}


/// Field with parent implementation.
class CvFieldWithParentImpl<T extends Object?>
    with CvFieldHelperMixin<T>
    implements CvFieldWithParent<T> {
  
  ......

  @override
  bool isSubtypeOf<SUPERTYPE>() => <T>[] is List<SUPERTYPE>;

  @override
  bool isSupertypeOf<SUBTYPE>() => <SUBTYPE>[] is List<T>;

  ......
}

Thanks for your reply.

I'm need at runtime check a type matches the field type.

exapmle.

if (field.isSubtypeOf<Enum?>()) {
    return value is! Enum ? TypeCodecRegistry.instance.getCodec(field.type)!.decode(value) : value;
}

[alextekartik]

Interesting. I have implemented your solution as a CvColumn extension in cv 1.1.10 just published.
(For now) you have to explicitely import import 'package:cv/utils/type_utils.dart';

import 'package:cv/cv.dart';
import 'package:cv/utils/type_utils.dart';

Future<void> main() async {
  void check(String message, bool value, bool expected) {
    print(
      '$message: $value${expected != value ? ' (expected: $expected)' : ''}',
    );
    assert(value == expected);
  }

  var fieldInt = CvField<int>('intField');

  check('intField isSubtypeOf<num>', fieldInt.isSubtypeOf<num>(), true);
  check('intField isSupertypeOf<num>', fieldInt.isSupertypeOf<num>(), false);

  var columnNum = CvColumnField<num>('numColumn');
  check('numColumn isSubtypeOf<int>', columnNum.isSubtypeOf<int>(), false);
  check('numColumn isSupertypeOf<int>', columnNum.isSupertypeOf<int>(), true);

  var fieldString = CvField<String>('stringField');
  check(
    'stringField isSubtypeOf<Object>',
    fieldString.isSubtypeOf<Object>(),
    true,
  );

  check(
    'stringField isSupertypeOf<Object>',
    fieldString.isSupertypeOf<Object>(),
    false,
  );
}

should print

intField isSubtypeOf<num>: true
intField isSupertypeOf<num>: false
numColumn isSubtypeOf<int>: false
numColumn isSupertypeOf<int>: true
stringField isSubtypeOf<Object>: true
stringField isSupertypeOf<Object>: false

[ebtone]

Interesting. I have implemented your solution as a CvColumn extension in cv 1.1.10 just published. (For now) you have to explicitely import import 'package:cv/utils/type_utils.dart';

import 'package:cv/cv.dart';
import 'package:cv/utils/type_utils.dart';

Future<void> main() async {
  void check(String message, bool value, bool expected) {
    print(
      '$message: $value${expected != value ? ' (expected: $expected)' : ''}',
    );
    assert(value == expected);
  }

  var fieldInt = CvField<int>('intField');

  check('intField isSubtypeOf<num>', fieldInt.isSubtypeOf<num>(), true);
  check('intField isSupertypeOf<num>', fieldInt.isSupertypeOf<num>(), false);

  var columnNum = CvColumnField<num>('numColumn');
  check('numColumn isSubtypeOf<int>', columnNum.isSubtypeOf<int>(), false);
  check('numColumn isSupertypeOf<int>', columnNum.isSupertypeOf<int>(), true);

  var fieldString = CvField<String>('stringField');
  check(
    'stringField isSubtypeOf<Object>',
    fieldString.isSubtypeOf<Object>(),
    true,
  );

  check(
    'stringField isSupertypeOf<Object>',
    fieldString.isSupertypeOf<Object>(),
    false,
  );
}

should print

intField isSubtypeOf<num>: true
intField isSupertypeOf<num>: false
numColumn isSubtypeOf<int>: false
numColumn isSupertypeOf<int>: true
stringField isSubtypeOf<Object>: true
stringField isSupertypeOf<Object>: false

Type checking cannot be achieved through mixin/extension, as field types are discarded at runtime in mobile device

[alextekartik]

Type checking cannot be achieved through mixin/extension, as field types are discarded at runtime in mobile device

That is what I though too, however the above example works fine even on release on Android for example. But the column needs to be properly typed.

[ebtone]

Type checking cannot be achieved through mixin/extension, as field types are discarded at runtime in mobile device

That is what I though too, however the above example works fine even on release on Android for example. But the column needs to be properly typed.

my Android device is not working