Dart Mappable Fork

This project is a fork of the dart_mappable package, with a key difference in the behavior of the copyWith method.

Difference

Null Assignment Handling:

This fork overrides the default copyWith behavior to ignore null assignments. This means that attempting to assign a null value to a property using copyWith will not alter the original value.

Example:

final person = Person(name: 'Tom', age: 20);

// assign age to null
print(person.copyWith(age: null));

The original behavior would result in:

Person(name: Tom, age: null)

But with the modification, age remains unchanged:

Person(name: Tom, age: 20)

Code Modification

The change is made within the FieldCopyWithData class:

Original

class FieldCopyWithData extends CopyWithData {
  FieldCopyWithData(this.fields);

  final Map<Symbol, dynamic> fields;

  @override
  V get<V>(Symbol name, {Object? or = $none}) {
    if (fields.containsKey(name) || or == $none) {
      return fields[name] as V;
    } else {
      return or as V;
    }
  }
}

Modified

class FieldCopyWithData extends CopyWithData {
  FieldCopyWithData(this.fields);

  final Map<Symbol, dynamic> fields;

  @override
  V get<V>(Symbol name, {Object? or = $none}) {
    var v = fields[name];
    if ((fields.containsKey(name) && v != null) || or == $none) {
      return v as V;
    } else {
      return or as V;
    }
  }
}