fix typo in my previous message and add documentation for default behavior

Author: Zooip

_site/guides/concepts/resources.html

@@ -231,7 +231,7 @@ <h4>
 <span class="k">end</span></code></pre></figure>
 
   <p>When guarding the <code class="highlighter-rouge">:readable</code> flag, the method can optionally accept the
-model instance and the of the attribute being serialized as arguments:</p>
+model instance and the name of the attribute being serialized as arguments:</p>
 
   <figure class="highlight"><pre><code class="language-ruby" data-lang="ruby"><span class="n">attribute</span> <span class="ss">:name</span><span class="p">,</span> <span class="ss">:string</span><span class="p">,</span> <span class="ss">readable: :allowed?</span>
 <span class="n">attribute</span> <span class="ss">:age</span><span class="p">,</span> <span class="ss">:integer</span><span class="p">,</span> <span class="ss">readable: :attribute_allowed?</span>
@@ -261,6 +261,16 @@ <h4>
 <span class="nb">self</span><span class="p">.</span><span class="nf">attributes_sortable_by_default</span> <span class="o">=</span> <span class="kp">false</span> <span class="c1"># default true</span>
 <span class="nb">self</span><span class="p">.</span><span class="nf">attributes_schema_by_default</span> <span class="o">=</span> <span class="kp">false</span> <span class="c1"># default true</span></code></pre></figure>
 
+  <p>As for resource defined guards, you can pass a symbol to guard the
+behavior globally. This can be used to globally delegate access control to a
+dedicated system.</p>
+
+  <figure class="highlight"><pre><code class="language-ruby" data-lang="ruby"><span class="nb">self</span><span class="p">.</span><span class="nf">attributes_readable_by_default</span> <span class="o">=</span> <span class="ss">:attribute_readable?</span> <span class="c1"># default true</span>
+
+<span class="k">def</span> <span class="nf">attribute_readable?</span><span class="p">(</span><span class="n">model_instance</span><span class="p">,</span> <span class="n">attribute_name</span><span class="p">)</span>
+  <span class="no">PolicyChecker</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">model_instance</span><span class="p">).</span><span class="nf">attribute_readable?</span><span class="p">(</span><span class="n">attribute_name</span><span class="p">)</span>
+<span class="k">end</span></code></pre></figure>
+
 <a class="anchor" id="customizing-display" />
   <a class="header" href="#customizing-display">
     <h4>

guides/concepts/resources.md

@@ -113,7 +113,7 @@ end
 {% endhighlight %}
 
 When guarding the `:readable` flag, the method can optionally accept the
-model instance and the of the attribute being serialized as arguments:
+model instance and the name of the attribute being serialized as arguments:
 
 {% highlight ruby %}
 attribute :name, :string, readable: :allowed?
@@ -142,6 +142,18 @@ self.attributes_sortable_by_default = false # default true
 self.attributes_schema_by_default = false # default true
 {% endhighlight %}
 
+As for resource defined guards, you can pass a symbol to guard the
+behavior globally. This can be used to globally delegate access control to a
+dedicated system.
+
+{% highlight ruby %}
+self.attributes_readable_by_default = :attribute_readable? # default true
+
+def attribute_readable?(model_instance, attribute_name)
+  PolicyChecker.new(model_instance).attribute_readable?(attribute_name)
+end
+{% endhighlight %}
+
 {% include h.html tag="h4" text="2.3 Customizing Display" a="customizing-display" %}
 
 Pass a block to `attribute` to customize display: