Merge pull request #24 from netglade/story/iterable-distinct

Add distinctBy iterable extension

packages/netglade_utils/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 1.3.0
+- Add `distinctBy` to iterable extensions.
+
 ## 1.2.0
 - Add `ifEmpty` and `ifBlank` to string extensions.
 - Remove typedefs. (private)

packages/netglade_utils/lib/src/extensions/extensions.dart

@@ -1,4 +1,5 @@
 export 'date_time_extensions.dart';
 export 'future_extensions.dart';
+export 'iterable_extensions.dart';
 export 'object_extensions.dart';
 export 'string_extensions.dart';

packages/netglade_utils/lib/src/extensions/iterable_extensions.dart

@@ -0,0 +1,16 @@
+import 'dart:core';
+
+typedef Selector<T, K> = K Function(T selectFrom);
+
+extension IterableExtensions<T> on Iterable<T> {
+  /// Returns an iterable containing only elements from the given collection having distinct keys returned by the given [selector] function.
+  /// If multiple elements have the same key, first element is returned.
+  Iterable<T> distinctBy<K>(Selector<T, K> selector) {
+    final result = <K, T>{};
+    for (final item in this) {
+      final _ = result.putIfAbsent(selector(item), () => item);
+    }
+
+    return result.values;
+  }
+}

packages/netglade_utils/pubspec.yaml

@@ -1,5 +1,5 @@
 name: netglade_utils
-version: 1.2.0
+version: 1.3.0
 description: Dart utils used internally at netglade.
 repository: https://github.com/netglade/flutter_core/tree/main/packages/netglade_utils
 issue_tracker: https://github.com/netglade/flutter_core/issues
@@ -12,6 +12,7 @@ environment:
 dependencies:
   characters: ^1.2.0
   clock: ^1.0.0
+  collection: ^1.0.0
   http: ^1.0.0
   mocktail: ^1.0.0
 

packages/netglade_utils/test/src/extensions/iterable_extensions_test.dart

@@ -0,0 +1,41 @@
+import 'package:collection/collection.dart';
+import 'package:netglade_utils/netglade_utils.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('distinct by', () {
+    test('distinct', () {
+      expect(
+        [
+          [1, 3],
+          [2, 5],
+          [3, 3],
+        ].distinctBy((e) => e.firstOrNull),
+        equals({
+          [1, 3],
+          [2, 5],
+          [3, 3],
+        }),
+      );
+    });
+
+    test('with duplicates', () {
+      expect(
+        [
+          [1, 3],
+          [2, 5],
+          [1, 6],
+          [1, 0],
+        ].distinctBy((e) => e.firstOrNull),
+        equals({
+          [1, 3],
+          [2, 5],
+        }),
+      );
+    });
+
+    test('empty', () {
+      expect(<int>[].distinctBy((e) => e * e), equals(<int>{}));
+    });
+  });
+}