CODEWITHSUNDEEP
flutterdartpackage
EvGeniy Ilyin
EvGeniy Ilyin

Reputation: 1929

Dart Package - How to hide internal methods in public classes?

I am developing a package on Flutter.

There are I have methods in classes that are useful only for the package itself, and not for the programmer who will import my package, is possible to hide this methods in public classes for further implementation?

I am trying use @internal annotation, but I can still see methods marked as internal outside of the package.

Example:

/// Base abstract class [ImageData]
abstract class ImageData  {
  /// Create [ImageData] instance.
  const ImageData();

  /// Create [ImageData] instance from [dto].
  ///
  /// by converting from [dto.ImageData].
  @internal
  factory ImageData.fromDto(dto.ImageData object) {
    switch (object.type) {
      case dto.ImageData_Type.pathType:
        return PathImageData(path: object.path);
      case dto.ImageData_Type.rawImageType:
        return RawImageData.fromDto(object.rawImage);
      default:
        throw const PluginInvokeException();
    }
  }

  /// Create [dto.ImageData] from current instance.
  @internal
  dto.ImageData toDto();

}

and in other inheritors from this ImageData

class RawImageData extends ImageData {
  /// Bytes of image.
  final Uint8List data;

  /// Describe type of [data] content.
  final RawImageDataType type;

  /// Wight of image
  final int width;

  /// Height of image
  final int height;

  /// Create [RawImageData] instance.
  const RawImageData({
    required this.data,
    required this.type,
    required this.width,
    required this.height,
  }) : super();

  /// Create [RawImageData] instance from [dto].
  ///
  /// by converting from [dto.RawImage].
  @internal
  factory RawImageData.fromDto(dto.RawImage object) {
    return RawImageData(
      data: Uint8List.fromList(object.raw),
      type: typeFromDtoEnum(object.type),
      width: object.size.width,
      height: object.size.height,
    );
  }

  @override
  @internal
  dto.ImageData toDto() {
    return dto.ImageData(
      type: dto.ImageData_Type.rawImageType,
      rawImage: toDtoRawImage(),
    );
  }

}

But I can still see methods marked as internal outside of the package. How do private this methods only for outside package namespaces?

Upvotes: 0

Views: 2236

Answers (1)

jamesdlin
jamesdlin

Reputation: 90145

Dart identifiers are either:

  • Public
  • Private to the library if prefixed with an underscore (_).

That's it.

Annotations such as @protected, @internal, etc. provide additional hints to the Dart analyzer. They are not enforced at compile-time (unless you explicitly make your build system fail on analysis warnings/errors) nor at runtime. (This also is why null-safe Dart needed a new required language keyword and could not use the old @required annotation.)

Either accept relying on analysis warnings or rename toDto to _toDto to make it private. Since private identifiers are private to the Dart library, that then would entail either:

  • Moving all your code into the same .dart file.
  • Explicitly declaring a Dart library with library and using part/part of to specify the .dart files that compose that library.

Another technique for hiding package-specific identifiers is to make them public but to place them in a .dart file internal to the package (with the expectation that clients will not explicitly import it). That's less useful for your case, however.

Upvotes: 3

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