Display a checkbox list instead of multiple select

Question

I have a model MyModel with a serialized attribute a, describing an array of symbols.

This code works :

<% form_for @my_         


        

Answer 1

There is another solution worth mentioning that makes it very easy to insert records into the database if you have a has_and_belongs_to_many or has_many through relationship by using the collection_check_boxes form helper. See documentation here.

<%= f.collection_check_boxes :mymodel_ids, MyModel::AS, :id, :name do |m| %>
  <%= m.check_box %> <%= m.label %>
<% end %>

Then, in the controller we would allow the mymodel_ids attribute:

params.require(:mymodel).permit(:name, mymodel_ids:[])

We can also set up a model validation to require that at least one of the checkboxes be checked:

validates :mymodel_ids, presence: true

An added benefit of this method is that if you later edit the mymodel record and uncheck one of the checkboxes, its record will be deleted from the many_to_many association table on save.