Added a From::first method

prewk · Feb 6, 2018 · 885831e · 885831e
1 parent f6ac3ae
commit 885831e
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diff --git a/spec/Option/FromSpec.php b/spec/Option/FromSpec.php
@@ -3,6 +3,7 @@
 namespace spec\Prewk\Option;
 
 use PhpSpec\ObjectBehavior;
+use Prewk\Option\OptionException;
 
 class FromSpec extends ObjectBehavior
 {
@@ -44,4 +45,11 @@ function it_creates_a_none_from_an_empty_value()
         $this::emptyable("0")->isNone()->shouldBe(true);
         $this::emptyable([])->isNone()->shouldBe(true);
     }
+
+    function it_creates_a_some_from_an_iterable_value()
+    {
+        $this::first([])->isNone()->shouldBe(true);
+        $this::first(["foo"])->isSome()->shouldBe(true);
+        $this->shouldThrow(OptionException::class)->during("first", [null]);
+    }
 }
diff --git a/src/Option/From.php b/src/Option/From.php
@@ -51,4 +51,23 @@ public static function emptyable($thing): Option
     {
         return !empty($thing) ? new Some($thing) : new None;
     }
+
+    /**
+     * Iterates over T and creates a Some<V> from the first item, returning None if T is empty
+     *
+     * @param $iterable Iterable T<V>
+     * @return Option Option<V>
+     */
+    public static function first($iterable): Option
+    {
+        if (!is_iterable($iterable)) {
+            throw new OptionException("Couldn't create Option from first item in non-iterable");
+        }
+
+        foreach ($iterable as $item) {
+            return new Some($item);
+        }
+
+        return new None;
+    }
 }