Add onceIf method (#35)

* test

* add onceif

* readme

README.md

@@ -142,6 +142,24 @@ public function has(string $name) : bool
  *
  * @return mixed
  */
+public function once($key, callable $callable)
+```
+
+### onceIf
+
+```php
+/**
+ * Use the "once" method only if the given condition is true.
+ *
+ * Otherwise, the callable will be executed.
+ *
+ * @param bool $shouldBlink
+ * @param $key
+ * @param callable
+ *
+ * @return mixed
+ */
+public function onceIf($shouldBlink, $key, callable $callable)
 ```
 
 ### all

src/Blink.php

@@ -305,6 +305,18 @@ public function once($key, callable $callable)
         return $this->get($key);
     }
 
+    /**
+     * Use the "once" method only if the given condition is true.
+     *
+     * Otherwise, the callable will be executed.
+     *
+     * @return mixed
+     */
+    public function onceIf($shouldBlink, $key, callable $callable)
+    {
+        return $shouldBlink ? $this->once($key, $callable) : $callable();
+    }
+
     protected function filterKeysStartingWith(array $values, string $startsWith): array
     {
         return array_filter($values, function ($key) use ($startsWith) {

tests/BlinkTest.php

@@ -481,4 +481,22 @@ public function it_can_perform_a_function_only_once()
             $this->assertSame($firstResult, $this->blink->once('random', $callable));
         }
     }
+
+    /** @test */
+    public function it_can_perform_a_function_only_once_conditionally()
+    {
+        $count = 0;
+        $callable = function () use (&$count) {
+            $count++;
+
+            return $count;
+        };
+
+        $this->assertSame(1, $this->blink->onceIf(false, 'key', $callable));
+        $this->assertSame(2, $this->blink->onceIf(true, 'key', $callable));
+        $this->assertSame(2, $this->blink->onceIf(true, 'key', $callable));
+        $this->assertSame(3, $this->blink->onceIf(false, 'key', $callable));
+        $this->assertSame(4, $this->blink->onceIf(false, 'key', $callable));
+        $this->assertSame(2, $this->blink->onceIf(true, 'key', $callable));
+    }
 }