How to select options from array with form_tag and checkboxes - arrays

Question

I have an array #sources that contains names (strings) of sources. In a view I want to list every source with a checkbox in a remote form. Then in the linked controller action I would like to have an array in the params hash, containing only those sources, that the user has checked before submitting.
I tried doing that manually, like so:
<%= form_tag select_sources_user_wordsearch_path(#user, #wordsearch), {method: :post, remote: true} do %>
<% #sources.each do |source| %>
<div class="form-group">
<div class="checkbox">
<label class="pull-left">
<input type="checkbox" class="pull-right"> <%=source%>
</label>
</div>
</div>
<% end %>
<div class="form-group">
<%= submit_tag "Start Search",id:"search_commit", class: "btn btn-primary" %>
</div>
<% end %>
But when submitting the form, I don't even see a params hash:
Started POST "/users/1/wordsearches/77/select_sources" for 127.0.0.1 at 2015-08-15 16:18:06 +0200
Processing by WordsearchesController#select_sources as JS
Parameters: {"utf8"=>"✓", "commit"=>"Start Search", "user_id"=>"1", "id"=>"77"}
So I was looking around to see what's going on with the form_tag helper and check_box_tag. And in check_box_tag's API page (see comments) I found that it is possible to pass a collection into it and receive the result of the selection in an array in the params hash. Basically, what I described above.
I am wondering how this would be done inside a form_tag for a remote form, with an array (instead of a collection)?
In the form_tag API page I couldn't find anything about how the data is transferred to the controller. In the check_box_tag there is nothing mentioned about how to handle collections.
Can anyone tell me how this is done "the Rails way"?
It has to be easier than I think..

Answer 1

First question: why don't you use the the form_for helper? Could be something like form_for #wordsearch, url: select_sources_user_wordsearch_path(#user, #wordsearch), {method: :post, remote: true} do.
You may also have a look at the collection_check_boxes helper in the API.
Afaik this can only be used with form_for and the corresponding form object.
<%= form_for #wordsearch do |form| %>
<%= form.collection_check_boxes(:source_ids, #sources, :id, :labeling_method ) %>
<% end %>
Assuming #sources is some kind of an object. In your case
<%= form_for #wordsearch do |form| %>
<%= form.collection_check_boxes(:sources, #sources, :to_s, :to_s ) %>
<% end %>
could work as well. (Did not try it!)
Another way would be to just send the values manually like so:
<% #sources.each do |source| -%>
<%= check_box_tag "wordsearch[sources][]", source -%>
<%= source -%>
<% end -%>
Hope this helps.