title: strong parameters not accepting array
body: <p>I have this in my view which is a multiselect checkbox</p>
  
  <p><strong>Model</strong></p>
  
  <pre><code>class User &lt; ActiveRecord::Base
    has_many :user_roles, :dependent =&gt; :destroy
    accepts_nested_attributes_for :user_roles, :allow_destroy =&gt; true
    has_many :roles, :through =&gt; :user_roles
  end
  </code></pre>
  
  <p><strong>view</strong> </p>
  
  <pre><code>&lt;%= check_box_tag 'user[role_ids][]', role.id, user.blank? ? nil : user.roles.include?(role) ,id: dom_id(role)%&gt;
  </code></pre>
  
  <p><strong>the strong parameters for this is written as</strong></p>
  
  <pre><code>  def user
      params.require(:user).permit(:first_name,{:role_ids =&gt; []})
    end
  </code></pre>
  
  <p>But on create it says</p>
  
  <pre><code>Processing by Admin::UsersController#create as HTML
    Parameters: {"utf8"=&gt;"✓", "authenticity_token"=&gt;"+y8iWya5KIILqS0embEUEZuClycXq0O9Q4pA+MnbM0g=", "user"=&gt;{"first_name"=&gt;"", "last_name"=&gt;"", "email"=&gt;"a@loclahost.com", "language"=&gt;"en", "access_level_id"=&gt;"1", "role_ids"=&gt;["", "1", "", "5", "", "", ""], "password"=&gt;"[FILTERED]", "password_confirmation"=&gt;"[FILTERED]"}, "commit"=&gt;"Create user"}
  
  Unpermitted parameters: role_ids
  Unpermitted parameters: role_ids
  Unpermitted parameters: role_ids
  Unpermitted parameters: role_ids
  </code></pre>
  
  <p>Any clue why is it not accepting the array of role_ids which is coming from form?</p>