Reder class for a collection_radio_buttons within simple_form - ruby-on-rails

Question

I am using simple_form to create a form within my Rails project.
<%= simple_form_for resource, :as => resource_name, :url => invitation_path(resource_name), :html => {:method => :post, id: 'invitations-form', class: 'invitations-form'} do |f| %>
<%= f.input :first_name, label: false, placeholder: "Family Member's First Name", input_html: { maxlength: 15, size: 40, value: nil } %>
<%= f.input :last_name, label: false, placeholder: "Family Member's Last", input_html: { maxlength: 15, size: 40, value: nil } %>
<%= f.input :email, label: false, placeholder: "Enter Email Address", input_html: { value: nil } %>
<div class="radio_buttons">
<%= f.label "#{:gender}:"%>
<%= f.collection_radio_buttons :gender, [["male", "male"] ,["female", "female"]], :first, :last %>
</div>
<%= f.input :invitation_relation, label: false, prompt: "I am this person's:", collection: relation_types, label_method: :humanize, input_html: { class: "browser-default dropmodule__input-select" } %>
<%= submit_tag "Send Invitation" %>
<% end %>
I have used the collection_radio_buttons method to create, well, a collection of radio buttons. I'm not sure this is relevant, but the reason I used this method instead of f.input :foo, as: :radio_buttons was due to the fact that the input method wasn't producing a label tag for me, which I think I could now produce using label_html. I'm not sure if this would be a viable alternative, but this bug is bothersome to me due to the time I've spent on it.
Here's the html generated output for the relevant div above:
<div class="radio_buttons">
<label class="string optional control-label" for="user_gender:">Gender:</label>
<span>
<input checked="checked" id="user_gender_male" name="user[gender]" type="radio" value="male">
<label class="collection_radio_buttons" for="user_gender_male">male</label>
</span>
<span>
<input id="user_gender_female" name="user[gender]" type="radio" value="female">
<label class="collection_radio_buttons" for="user_gender_female">female</label>
</span>
</div>
I need the input tag for each radio_button to contain a class of "with-gap", like so:
<input checked="checked" id="user_gender_male" class="with-gap" name="user[gender]" type="radio" value="male">
and
<input id="user_gender_female" class="with-gap" name="user[gender]" type="radio" value="female">
but I have been unsuccessful. Although I really want to solve the issue by placing the class within the label of the collection_radio_buttons method, if there is an alternative within simple_form please show this as a solution.

Answer 1

OK, I found the answer here:
https://stackoverflow.com/a/30619068/4379077
What I needed to do was add an item_wrapper_class as the 5th argument to the method. It doesn't look like it's optional. When I try to remove it from the argument list my class argument (the 6th arg in the method) gets ignored. Here's the final input:
<div class="radio_buttons">
<%= f.label "#{:gender}:"%>
<%= f.collection_radio_buttons :gender, [["male", "male"] ,["female", "female"]], :first, :last, {:item_wrapper_class => 'foo-bar'}, {:class => "with-gap" } %>
</div>
and final output:
<div class="radio_buttons">
<label class="string optional control-label" for="user_gender:">Gender:</label>
<span class="foo-bar">
<input checked="checked" class="with-gap" id="user_gender_male" name="user[gender]" type="radio" value="male">
<label class="collection_radio_buttons" for="user_gender_male">male</label >
</span>
<span class="foo-bar">
<input class="with-gap" id="user_gender_female" name="user[gender]" type="radio" value="female">
<label class="collection_radio_buttons" for="user_gender_female">female</label>
</span>
</div>
If anyone knows how to make the inline_wrapper_class optional please let me know.