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  1. lib/
  2. test/
  3. .gitignore
  4. .metadata
  8. pubspec.yaml


This package provides a base class for platform interfaces of federated flutter plugins.

Platform implementations should extend their platform interface classes rather than implement it as newly added methods to platform interfaces are not considered as breaking changes. Extending a platform interface ensures that subclasses will get the default implementations from the base class, while platform implementations that implements their platform interface will be broken by newly added methods.

This class package provides common functionality for platform interface to enforce that they are extended and not implemented.

Sample usage:

abstract class UrlLauncherPlatform extends PlatformInterface {
  UrlLauncherPlatform() : super(token: _token);

  static UrlLauncherPlatform _instance = MethodChannelUrlLauncher();

  static final Object _token = Object();

  static UrlLauncherPlatform get instance => _instance;

  /// Platform-specific plugins should set this with their own platform-specific
  /// class that extends [UrlLauncherPlatform] when they register themselves.
  static set instance(UrlLauncherPlatform instance) {
    PlatformInterface.verify(instance, _token);
    _instance = instance;


This guarantees that UrlLauncherPlatform.instance cannot be set to an object that implements UrlLauncherPlatform (it can only be set to an object that extends UrlLauncherPlatform).

Mocking or faking platform interfaces

Test implementations of platform interfaces, such as those using mockito's Mock or test's Fake, will fail the verification done by verify. This package provides a MockPlatformInterfaceMixin which can be used in test code only to disable the extends enforcement.

For example, a Mockito mock of a platform interface can be created with:

class UrlLauncherPlatformMock extends Mock
   with MockPlatformInterfaceMixin
   implements UrlLauncherPlatform {}