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POPopulating Checkboxes on Rails from DB
 

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  1. POPopulating Checkboxes on Rails from DB
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    <p>I am just starting to learn about Rails (ver. 3), and I am trying to create a user registration form with checkbox options for their interests, which may be 0 or more selections. I generated a User scaffold, and an interest model. I seeded the interests table in Postgresql with data:</p> <pre><code> Table "public.interests" Column | Type | Modifiers ------------+--------------------+------------------------------------------------ id | integer | not null default nextval('interests_id_seq'::regclass) interest | character varying(40) | created_at | timestamp without time zone | updated_at | timestamp without time zone | Indexes: "interests_pkey" PRIMARY KEY, btree (id) </code></pre> <p>The view has:</p> <pre><code>&lt;div class="form_row"&gt; &lt;label for="interest_ids[]"&gt;Interests:&lt;/label&gt; &lt;% for interest in Interest.find(:all) do %&gt; &lt;br&gt;&lt;%= check_box_tag 'interest_ids[]', interest.id, @model.interest_ids.include?(interest.id) %&gt; &lt;%= interest.name.humanize %&gt; &lt;% end %&gt; &lt;/div&gt; </code></pre> <p>(based on <a href="https://stackoverflow.com/questions/621340/checkboxes-on-rails">Checkboxes on Rails</a>)</p> <p>The model interest.rb has:</p> <pre><code>class Interest &lt; ActiveRecord::Base has_and_belongs_to_many :users end </code></pre> <p>The users controller users_controller.rb has:</p> <pre><code> def new @user = User.new respond_to do |format| format.html # new.html.erb format.xml { render :xml =&gt; @user } end end </code></pre> <p>When I view the page I get:</p> <pre><code>undefined method `interest_ids' for nil:NilClass </code></pre> <p>Can someone tell me what's wrong? Thanks.</p>
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    1. COWhat is @model supposed to be? I don't see it defined anywhere. It looks like maybe it should be @user instead? Another issue is that you're using HABTM, where its preferable to use Has Many Through.
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      1. USPreston Marshall
    2. COSomequestions: 1. The view you have shown is for which controller? I suppose it is for InterestsController.2 . Your variable `@model` should be of which type? In the view, the `@model` gets the message `interest_ids`, and if the `@model` is not filled, it is `nil` automatically. That should explain the error message. Some model class has to implement `interest_ids`.
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      1. USmliebelt
 

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