Meai1 · August 11, 2018 16:40 · Aug 11, 2018
diff --git a/generics.dart b/generics.dart
@@ -0,0 +1,34 @@
+library petitparser.core.actions.action;
+
+import 'package:dart_server_test/src/core/combinators/delegate.dart';
+import 'package:dart_server_test/src/core/contexts/context.dart';
+import 'package:dart_server_test/src/core/contexts/result.dart';
+import 'package:dart_server_test/src/core/parser.dart';
+
+/// Typed action callback.
+typedef R ActionCallback<T, R>(T value);
+
+/// A parser that performs a transformation with a given function on the
+/// successful parse result of the delegate.
+class ActionParser<T, R> extends DelegateParser<R> {
+  final ActionCallback<T, R> callback;
+
+  ActionParser(Parser<T> delegate, this.callback) : super(delegate);
+
+  @override
+  Result<R> parseOn(Context context) {
+    Result<T> result = delegate.parseOn(context);
+    if (result.isSuccess) {
+      return result.success(callback(result.value));
+    } else {
+      return result.failure(result.message);
+    }
+  }
+
+  @override
+  ActionParser<T, R> copy() => ActionParser<T, R>(delegate, callback);
+
+  @override
+  bool hasEqualProperties(ActionParser<T, R> other) =>
+      super.hasEqualProperties(other) && callback == other.callback;
+}