Implement flatMap for Option (#64)

* Implement flatMap for Option * code style fixes
munusphp · Dec 11, 2022 · 4567ce0 · 4567ce0
1 parent f854498
commit 4567ce0
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diff --git a/src/Control/Option.php b/src/Control/Option.php
@@ -77,6 +77,20 @@ public function map(callable $mapper)
  return $this->isEmpty() ? self::none() : self::some($mapper($this->get()));
  }
 
+ /**
+ * Maps the value to a new Option if this is a Some, otherwise returns None.
+ *
+ * @template U
+ *
+ * @param callable(T):Option<U> $mapper
+ *
+ * @return Option<U>
+ */
+ public function flatMap(callable $mapper)
+ {
+ return $this->isEmpty() ? self::none() : $mapper($this->get());
+ }
+
  public function isSingleValued(): bool
  {
  return true;

diff --git a/tests/Control/OptionTest.php b/tests/Control/OptionTest.php
@@ -63,6 +63,23 @@ public function testMap(): void
  self::assertEquals('MUNUS', $option->map('strtoupper')->get());
  }
 
+ public function testFlatMapSome(): void
+ {
+ $option = Option::of('munus');
+
+ self::assertInstanceOf(Option::class, $option->flatMap(fn (string $value) => Option::some($value)));
+ self::assertEquals('munus', $option->flatMap(fn (string $value) => Option::some($value))->get());
+ self::assertEquals('2', $option->flatMap(fn () => Option::of('2'))->get());
+ self::assertTrue(Option::none()->equals($option->flatMap(fn () => Option::none())));
+ }
+
+ public function testFlatMapNone(): void
+ {
+ $option = Option::none();
+
+ self::assertTrue(Option::none()->equals($option->flatMap(fn (string $value) => Option::some($value))));
+ }
+
  public function testOptionForEach(): void
  {
  $lazy = Lazy::ofValue(1);