fetch pokemon with validation example

examples/poke_api/lib/constants.dart

@@ -0,0 +1,7 @@
+abstract interface class Constants {
+  static const int minimumPokemonId = 1;
+  static const int maximumPokemonId = 898;
+
+  static String requestAPIUrl(int pokemonId) =>
+      'https://pokeapi.co/api/v2/pokemon/$pokemonId';
+}

examples/poke_api/lib/main.dart

@@ -0,0 +1,51 @@
+import 'dart:convert';
+
+import 'package:fpdart/fpdart.dart';
+import 'package:poke_api/constants.dart';
+import 'package:poke_api/pokemon.dart';
+import 'package:poke_api/pokemon_error.dart';
+
+abstract interface class HttpClient {
+  String get(Uri uri);
+}
+
+Effect<(HttpClient, JsonCodec), PokemonError, Pokemon> program(
+  String pokemonId,
+) =>
+    Effect.gen(($) async {
+      final (client, json) = await $(Effect.env());
+
+      final id = await $(
+        Either.fromNullable(
+          int.tryParse(pokemonId),
+          PokemonIdNotInt.new,
+        ),
+      );
+
+      if (id < Constants.minimumPokemonId && id > Constants.maximumPokemonId) {
+        return await $(Effect.fail(const InvalidPokemonIdRange()));
+      }
+
+      final uri = Uri.parse(Constants.requestAPIUrl(id));
+      final body = await $(Effect.tryCatch(
+        execute: () => client.get(uri),
+        onError: (_, __) => const GetPokemonRequestError(),
+      ));
+
+      final bodyJson = await $(Either.tryCatch(
+        execute: () => json.decode(body),
+        onError: (_, __) => const PokemonJsonDecodeError(),
+      ));
+
+      final bodyJsonMap = await $<Map<String, dynamic>>(
+        Either.safeCastStrict(
+          bodyJson,
+          (value) => const PokemonJsonInvalidMap(),
+        ),
+      );
+
+      return $(Effect.tryCatch(
+        execute: () => Pokemon.fromJson(bodyJsonMap),
+        onError: (_, __) => const PokemonInvalidJsonModel(),
+      ));
+    });

examples/poke_api/lib/pokemon.dart

@@ -0,0 +1,20 @@
+class Pokemon {
+  final int id;
+  final String name;
+  final int height;
+  final int weight;
+
+  const Pokemon({
+    required this.id,
+    required this.name,
+    required this.height,
+    required this.weight,
+  });
+
+  factory Pokemon.fromJson(Map<String, Object?> json) => Pokemon(
+        id: json['id'] as int,
+        name: json['name'] as String,
+        height: json['height'] as int,
+        weight: json['weight'] as int,
+      );
+}

examples/poke_api/lib/pokemon_error.dart

@@ -0,0 +1,27 @@
+sealed class PokemonError {
+  const PokemonError();
+}
+
+class PokemonIdNotInt extends PokemonError {
+  const PokemonIdNotInt();
+}
+
+class InvalidPokemonIdRange extends PokemonError {
+  const InvalidPokemonIdRange();
+}
+
+class GetPokemonRequestError extends PokemonError {
+  const GetPokemonRequestError();
+}
+
+class PokemonJsonDecodeError extends PokemonError {
+  const PokemonJsonDecodeError();
+}
+
+class PokemonJsonInvalidMap extends PokemonError {
+  const PokemonJsonInvalidMap();
+}
+
+class PokemonInvalidJsonModel extends PokemonError {
+  const PokemonInvalidJsonModel();
+}

examples/poke_api/pubspec.yaml

@@ -0,0 +1,18 @@
+name: poke_api
+description: >
+  Example of using fpdart to fetch pokemon from pokeapi with validation.
+version: 2.0.0
+homepage: https://www.sandromaglione.com/
+repository: https://github.com/SandroMaglione/fpdart
+publish_to: "none"
+
+environment:
+  sdk: ">=3.3.0 <4.0.0"
+
+dependencies:
+  fpdart:
+    path: ../../packages/fpdart
+
+dev_dependencies:
+  lints: ^2.0.1
+  test: ^1.23.1

packages/fpdart/lib/src/either.dart

@@ -15,12 +15,12 @@ sealed class Either<L, R> extends IEffect<Never, L, R> {
   factory Either.fromNullable(R? r, L Function() onNull) =>
       r != null ? Right(r) : Left(onNull());
 
-  factory Either.tryCatch(
-    R Function() run,
-    L Function(Object o, StackTrace s) onError,
-  ) {
+  factory Either.tryCatch({
+    required R Function() execute,
+    required L Function(Object o, StackTrace s) onError,
+  }) {
     try {
-      return Right(run());
+      return Right(execute());
     } catch (e, s) {
       return Left(onError(e, s));
     }