title: How to permit array of array in rails
body: <p>I have one request where one of the fields is array of array.
  parameters</p>
  
  <pre><code>{ 
    "product" =&gt; { 
      "pitch_points"=&gt;{
        "adwords"=&gt;{
          "search"=&gt;{
            "short"=&gt;["qwe"], 
            "long"=&gt;[["asdadas", "dasdasdas"]] 
          } 
        } 
      } 
    } 
  }
  </code></pre>
  
  <p>How can we permit this long key?</p>
  
  <p>I have done like this</p>
  
  <pre><code>params.require(:product).permit( 
    pitch_points: [
      adwords: [ 
        search: [ 
          short: [], 
          long: [] 
        ] 
      ] 
    ]
  )
  </code></pre>
  
  <p>.my output is </p>
  
  <pre><code>{
    "pitch_points"=&gt;{
      "adwords"=&gt;{
        "search"=&gt;{
          "short"=&gt;["qwe"], 
          "long"=&gt;[]
        }
      }
    }
  }
  </code></pre>
  
  <p>but output is empty long.</p>