Question

In my database I have two tables that has a many-to-many relationship, and by that reason I’ve created a relationship table.

Projects
Users
Project_users <-- members of a project

I’m working on the view for editing a project, which contain of a form with all the project fields, and for the members of a project I render out checkboxes. This works, but with the code below all the checkboxes is checked, even for the users that’s not members of the project.

So, how should I change the code so only the checkboxes for the current members of the project gets checked?

edit project view:

<%= form_for @project do |f| %>
    ...
        the rest of the form
    ...
    <div class="checkbox">
        <% @members.each do |user| %>
            <%= check_box_tag "project[members][]", user.id, '1', :id => "user_#{user.id}" %> 
            <%= label_tag "user_#{user.id}", user.first_name + ' ' + user.last_name, :class => "checkbox" %>
        <% end %>
    </div>
    ...
        the rest of the form
    ...
<% end %>

projects controller:

...
def edit
    @project = Project.find(params[:id])
    @members = @project.users
end
...

Answer 1

The third argument to the check_box_tag is the boolean for the check(ed) state:

See the doc: check_box_tag(name, value = "1", checked = false, options = {})

In your case:

<% should_be_checked = @project.users.include?(user) %>
<%= check_box_tag "project[members][]", user.id, should_be_checked, :id => "user_#{user.id}" %>