Add NullableObjects

sugar/lib/core.dart

@@ -48,7 +48,7 @@
 /// * [Strings]
 ///
 /// ## Miscellaneous
-///
+/// * [NullableObjects]
 /// * [Disposable]
 /// * [StringBuffers]
 library sugar.core;
@@ -59,6 +59,7 @@ import 'package:sugar/src/core/comparables.dart';
 import 'package:sugar/src/core/disposable.dart';
 import 'package:sugar/src/core/equality.dart';
 import 'package:sugar/src/core/functions.dart';
+import 'package:sugar/src/core/nullable.dart';
 import 'package:sugar/src/core/result.dart';
 import 'package:sugar/src/core/string_buffers.dart';
 import 'package:sugar/src/core/strings.dart';
@@ -69,6 +70,7 @@ export 'src/core/comparables.dart';
 export 'src/core/disposable.dart';
 export 'src/core/equality.dart';
 export 'src/core/functions.dart';
+export 'src/core/nullable.dart';
 export 'src/core/result.dart';
 export 'src/core/string_buffers.dart';
 export 'src/core/strings.dart';

sugar/lib/math.dart

@@ -6,17 +6,23 @@
 /// * [Integers] - functions that ceil, floor and round numbers.
 /// * [Doubles] - function for fuzzy equality
 ///
+/// ## Nullable numeric operations
+/// * [NullableNumbers] - overloaded operators for working with nullable numbers.
+/// * [NullableIntegers] - overloaded operators for working with nullable integers.
+/// * [NullableDoubles] - overloaded operators for working with nullable doubles.
+///
 /// ## Random
 /// * [Randoms] - functions for using [Random]
 /// * [FakeRandom] - a fake [Random] implementation for testing
 library sugar.math;
 
 import 'dart:math';
 
+import 'package:sugar/src/math/nullable_numbers.dart';
 import 'package:sugar/src/math/numbers.dart';
 import 'package:sugar/src/math/random.dart';
 
 export 'src/math/arithmetic_exception.dart';
-export 'src/math/nullable.dart';
+export 'src/math/nullable_numbers.dart';
 export 'src/math/numbers.dart';
 export 'src/math/random.dart';

sugar/lib/src/core/nullable.dart

@@ -0,0 +1,18 @@
+/// Provides functions for casting nullable [Object]s.
+extension NullableObjects on Object? {
+
+  /// Casts `this` to [T] if it is a [T], and returns `null` otherwise.
+  ///
+  /// ```dart
+  /// final num foo = 1;
+  /// foo.as<int>(); // 1
+  ///
+  /// 'string'.as<int>(); // null
+  /// null.as<int>(); // null
+  /// ```
+  T? as<T extends Object>() {
+    final self = this;
+    return self is T ? self : null;
+  }
+
+}

sugar/test/src/core/nullable_test.dart

@@ -0,0 +1,17 @@
+import 'package:test/test.dart';
+import 'package:sugar/sugar.dart';
+
+void main() {
+  group('NullableObjects', () {
+    group('as()', () {
+      test('exact type', () {
+        const num foo = 1;
+        expect(foo.as<int>(), 1);
+      });
+
+      test('different type', () => expect('string'.as<int>(), null));
+
+      test('null', () => expect(null.as<int>(), null));
+    });
+  });
+}