add withDefault to Maybe

marcosh · Oct 16, 2021 · ae0dab4 · ae0dab4
1 parent 5593f82
commit ae0dab4
Show file tree

Hide file tree

Showing 2 changed files with 28 additions and 0 deletions.
diff --git a/spec/MaybeSpec.php b/spec/MaybeSpec.php
@@ -29,6 +29,18 @@
         expect($result)->toEqual(84);
     });
 
+    it('uses the default value when extracting a Nothing', function () {
+        $maybe = Maybe::nothing();
+
+        expect($maybe->fromMaybe(42))->toBe(42);
+    });
+
+    it('return the inner value when extracting a Just', function () {
+        $maybe = Maybe::just(42);
+
+        expect($maybe->fromMaybe(37))->toBe(42);
+    });
+
     it('maps a nothing to a nothing', function () {
         $maybe = Maybe::nothing();
 

diff --git a/src/Maybe.php b/src/Maybe.php
@@ -111,6 +111,22 @@ public function eval(
         return $ifNothing;
     }
 
+    /**
+     * @param A $a
+     * @return A
+     */
+    public function fromMaybe($a)
+    {
+        return $this->eval(
+            $a,
+            /**
+             * @param A $a
+             * @return A
+             */
+            fn($a) => $a
+        );
+    }
+
     /**
      * @template B
      * @param Functor<MaybeBrand> $functor