+ iterable distinct

Author: ivicicm

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 +1,20 @@
+import 'dart:core';
+
+import 'package:collection/collection.dart';
+
+typedef Selector<T, K> = K Function(T selectFrom);
+
+extension IterableExtensions<T> on Iterable<T> {
+  /// Returns a set containing only distinct elements from the given collection.
+  Set<T> distinct() {
+    return toSet();
+  }
+
+  /// Returns a list 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) {
+    return groupBy<T, K>(this, selector)
+        .values
+        // ignore: avoid-unsafe-collection-methods, groupBy returns non-empty lists
+        .map((e) => e.first);
+  }
+}

packages/netglade_utils/pubspec.yaml

@@ -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 +1,32 @@
+import 'package:netglade_utils/netglade_utils.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('distinct', () {
+    test('distinct', () {
+      expect([1, 2, 3].distinct(), equals({1, 2, 3}));
+    });
+
+    test('with duplicates', () {
+      expect([2, 4, 4, 5, 6, 6, 6].distinct(), equals({2, 4, 5, 6}));
+    });
+
+    test('empty', () {
+      expect(<int>[].distinct(), equals(<int>{}));
+    });
+  });
+
+  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>{}));
+    });
+  });
+}