Add enum argument.

Author: panvid

README.md

@@ -171,4 +171,16 @@ $person1 = new ArrayArgument('', [new Argument('name', 'Hans'), new Argument('ag
 $person2 = new ArrayArgument('', [new Argument('name', 'Max'), new Argument('age', 20)]);
 
 $persons = new ArrayArgument('persons', [$person1, $person2]);
-```
+```
+
+### Enum arguments
+To create enum arguments it should look like this:
+
+```php
+<?php
+declare(strict_types=1);
+
+use GraphQL\RequestBuilder\EnumArgument;
+
+$person1 = new EnumArgument('EnumAttribute', 'EnumValue');
+```

src/Argument.php

@@ -19,7 +19,7 @@ class Argument implements ArgumentInterface
     protected $name;
 
     /** @var int|float|string|bool|Argument[]|Argument The value of the argument. */
-    private $value;
+    protected $value;
 
     /**
      * @inheritdoc

src/ArrayArgument.php

@@ -5,7 +5,7 @@
 
 /**
  * @author  david.pauli
- * @package GraphQLTest\RequestBuilder
+ * @package GraphQL\RequestBuilder
  * @since   15.08.2018
  */
 class ArrayArgument extends Argument

src/EnumArgument.php

@@ -0,0 +1,28 @@
+<?php
+declare(strict_types=1);
+
+namespace GraphQL\RequestBuilder;
+
+/**
+ * @author  david.pauli
+ * @package GraphQL\RequestBuilder
+ * @since   29.08.2018
+ */
+class EnumArgument extends Argument
+{
+    /**
+     * @inheritdoc
+     */
+    public function __toString(): string
+    {
+        switch (gettype($this->value)) {
+            case 'string':
+                $value = '' . $this->value . '';
+                break;
+            default:
+                $value =  null;
+        }
+
+        return $value === null ? '': $this->name . ':' . $value;
+    }
+}

tests/EnumArgumentTest.php

@@ -0,0 +1,29 @@
+<?php
+declare(strict_types=1);
+
+namespace GraphQLTest\RequestBuilder;
+
+use GraphQL\RequestBuilder\EnumArgument;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @author  david.pauli
+ * @package GraphQLTest\RequestBuilder
+ * @since   29.08.2018
+ */
+class EnumArgumentTest extends TestCase
+{
+    private const ARGUMENT_NAME = 'argumentName';
+    private const ENUM_VALUE = 'enumValue';
+
+    public function testToStringEnum(): void
+    {
+        $argument = new EnumArgument(self::ARGUMENT_NAME, self::ENUM_VALUE);
+
+        static::assertEquals(
+            self::ARGUMENT_NAME . ':' . self::ENUM_VALUE,
+            (string) $argument,
+            'Enum should be correct created.'
+        );
+    }
+}