Add a fluent way to send route variables to DataTable service class.

Fix #2 and yajra/laravel-datatables#845.

src/Services/DataTable.php

@@ -71,6 +71,13 @@ abstract class DataTable implements DataTableContract, DataTableButtonsContract
      */
     protected $filename = '';
 
+    /**
+     * Custom attributes set on the class.
+     *
+     * @var array
+     */
+    protected $attributes = [];
+
     /**
      * DataTable constructor.
      *
@@ -360,6 +367,39 @@ public function addScope(DataTableScopeContract $scope)
         return $this;
     }
 
+    /**
+     * Set a custom class attribute.
+     *
+     * @param mixed $key
+     * @param mixed|null $value
+     * @return $this
+     */
+    public function with($key, $value = null)
+    {
+        if (is_array($key)) {
+            $this->attributes = array_merge($this->attributes, $key);
+        } else {
+            $this->attributes[$key] = $value;
+        }
+
+        return $this;
+    }
+
+    /**
+     * Dynamically retrieve the value of an attribute.
+     *
+     * @param string $key
+     * @return mixed|null
+     */
+    public function __get($key)
+    {
+        if (array_key_exists($key, $this->attributes)) {
+            return $this->attributes[$key];
+        }
+
+        return null;
+    }
+
     /**
      * Apply query scopes.
      *