#117 add: Iterable.modifyWhere() and Iterable.modifyFirstWhere()

README.md

@@ -93,6 +93,22 @@ final increasingSubSequences = list.chunkWhile((a, b) => a + 1 == b);
 `splitWhen` is the opposite of `chunkWhile` that starts a new chunk every time
 the predicate _didn't_ match.
 
+### .modifyWhere()
+
+Applies a given modifier as long as predicate is true:
+```dart
+final values = [1, 2, 3];
+values.modifyWhere((v) => v > 1, (v) => -v); // [1, -2, -3]
+```
+
+### .modifyFirstWhere()
+
+Applies the modifier to the first element that matches predicate:
+```dart
+final values = [1, 2, 3];
+values.modifyWhere((v) => v > 1, (v) => -v); // [1, -2, 3]
+```
+
 ## String
 
 ### .capitalize

lib/src/iterable.dart

@@ -1381,3 +1381,40 @@ extension IterableStartsWithExtension<E> on Iterable<E> {
     return true;
   }
 }
+
+extension IterableModifyWhereExtension<T> on Iterable<T> {
+  /// Applies [modifier] to all elements matching the given [predicate]
+  ///
+  /// ```dart
+  /// final values = [1, 2, 3];
+  /// values.modifyWhere((v) => v > 1, (v) => -v); // [1, -2, -3]
+  /// ```
+  Iterable<T> modifyWhere(
+    bool Function(T) predicate,
+    T Function(T) modifier,
+  ) {
+    return map((item) => predicate(item) ? modifier(item) : item);
+  }
+}
+
+extension IterableModifyFirstWhereExtension<T> on Iterable<T> {
+  /// Applies [modifier] to the first element matching the given [predicate]
+  ///
+  /// ```dart
+  /// final values = [1, 2, 3];
+  /// values.modifyWhere((v) => v > 1, (v) => -v); // [1, -2, 3]
+  /// ```
+  Iterable<T> modifyFirstWhere(
+    bool Function(T) predicate,
+    T Function(T) modifier,
+  ) {
+    bool modified = false;
+    return modifyWhere(
+      (v) => !modified && predicate(v),
+      (v) {
+        modified = true;
+        return modifier(v);
+      },
+    );
+  }
+}

test/iterable_test.dart

@@ -1003,5 +1003,47 @@ void main() {
       expect([null, 1, 2, 3].startsWith([null, 1]), true);
       expect([1, null, 3].startsWith([1, null]), true);
     });
+
+    test('.modifyWhere()', () {
+      final items = [1, 2, 3, 4, 5, 6];
+
+      expect(
+        items.modifyWhere((v) => v < 3, (i) => -i),
+        [-1, -2, 3, 4, 5, 6],
+      );
+      expect(
+        items.modifyWhere((v) => v > 3, (i) => -i),
+        [1, 2, 3, -4, -5, -6],
+      );
+      expect(
+        items.modifyWhere((v) => v < 0, (i) => -i),
+        [1, 2, 3, 4, 5, 6],
+      );
+      expect(
+        items.modifyWhere((v) => v > 0, (i) => i * 2),
+        [2, 4, 6, 8, 10, 12],
+      );
+    });
+
+    test('.modifyFirstWhere()', () {
+      final items = [1, 2, 3, 4, 5, 6];
+
+      expect(
+        items.modifyFirstWhere((v) => v < 3, (i) => -i),
+        [-1, 2, 3, 4, 5, 6],
+      );
+      expect(
+        items.modifyFirstWhere((v) => v > 3, (i) => -i),
+        [1, 2, 3, -4, 5, 6],
+      );
+      expect(
+        items.modifyFirstWhere((v) => v < 0, (i) => -i),
+        [1, 2, 3, 4, 5, 6],
+      );
+      expect(
+        items.modifyFirstWhere((v) => v > 0, (i) => i * 2),
+        [2, 2, 3, 4, 5, 6],
+      );
+    });
   });
 }