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Consider the following form which has only one input role_id
which is accepted through collection_radio_button
.
1<%= form_for(@user) do |f| %>
2 <%= f.collection_radio_buttons :role_id, @roles, :id, :name %>
3 <div class="actions">
4 <%= f.submit %>
5 </div>
6<% end %>
In the controller, we can access role_id
using the strong parameters.
1def user_params
2 params.require(:user).permit(:role_id)
3end
When we try to submit this form without selecting any radio button in Rails 4.x,
we will get 400 Bad Request
error with following message.
1ActionController::ParameterMissing (param is missing or the value is empty: user):.
This is because following parameters were sent to server in Rails 4.x .
1Parameters: {"utf8"=>"✓", "authenticity_token"=>"...", "commit"=>"Create User"}
According to HTML specification, when multiple parameters are passed to collection_radio_buttons
and no option is selected, web browsers do not send any value to the server.
Rails 5
adds hidden field on the collection_radio_buttons
to avoid raising an error when the only input on the form is collection_radio_buttons
.
The hidden field has the same name as collection radio button and has blank value.
Following parameters will be sent to server in Rails 5 when above user form is submitted:
1Parameters: {"utf8"=>"✓", "authenticity_token"=>"...", "user"=>{"role_id"=>""}, "commit"=>"Create User"}
In case we don't want the helper to generate this hidden field, we can specify include_hidden: false
.
1<%= f.collection_radio_buttons :role_id, Role.all, :id, :name, include_hidden: false %>