multiple select - ruby-on-rails

Question

I am trying to create a form that allows to assign multiple projectmembers to a project.
(User and Project model being related through UserProject )
here is my view:
<div class="field">
<%= fields_for :projectmember do |u| %>
<%= u.label :projectmember %><br />
<%= select_tag :projectmember, options_for_select(User.all.collect {|u| [u.id, u.lastname]}, :projectmember),:multiple => true, :prompt => 'Select Person' %>
<% end %>
</div>
i have put the projectmember tag all over the place but i can't figure it out how to save this field projectmember into my db projects and user_projects !!??
my projects_controller :
def new
#project = Project.new
#user_project=UserProject.new
#user=User.all
#user_lastnames = User.all.collect do |u|
u.lastname
end
respond_to do |format|
format.html # new.html.erb
format.json { render json: #project }
end
end
and
def create
#project = Project.new(params[:project])
respond_to do |format|
if #project.save
format.html { redirect_to #project, notice: 'Project was successfully created.' }
format.json { render json: #project, status: :created, location: #project }
#user_project=UserProject.create(:project_id => #project.id, :user_id => #project.projectmember)
else
format.html { render action: "new" }
format.json { render json: #project.errors, status: :unprocessable_entity }
end
end
end
After creating one instance, the command using the console : #project=Project.all gives :
Project id: 55, projectname: "fdfd", projectdescription: "fdfd", projectheader: "5", projectmember: nil, projecttypename: "dffd">]

Answer 1

Assuming your associations are something like this:
class Project < ActiveRecord::Base
has_many :project_users
has_many :users, :through=>:project_users
end
...for your project form, use the following helper with the "name" option (:name=>'project[user_ids][]') to pass the selected ids to your controller:
<%= select_tag :user_ids, options_for_select(User.all.collect {|u| [u.lastname, u.id]}),:multiple => true, :prompt => 'Select Person', :name=>'project[user_ids][]' %>
That will give you the selected ids in the params and then you'll have to hook up your controller actions to assign them. For example:
def create
#project = Project.new(params[:project])
users = User.find(params[:project][:user_ids]) rescue []
#project.users = users
if #project.save
...
else
...
end
end
def update
#project = Project.find(params[:id])
users = User.find(params[:project][:user_ids]) rescue []
#project.users = users
if #project.update_attributes(params[:project])
...
else
...
end
end
In order to get the selected items to re-select when you render the edit form, I'm assuming you'd have to add that as an argument to the options_for_select method. Not exactly sure about that. An alternative to doing all of the above would be to use checkboxes to select the users since the checked could be set for each assigned user when the form renders. Good luck.

Answer 2

my model was indeed like that :
class Project < ActiveRecord::Base
has_many :project_users
has_many :users, :through=>:project_users
attr_accessible :colourcode, :projectdescription, :user_id, :projectname, :projectheader, :projectmember, :projecttypename
end
i have needed to change in my view ( else Can't mass-assign protected attributes):
<%= select_tag :user_ids, options_for_select(User.all.collect {|u| [u.lastname, u.id]}),:multiple => true, :prompt => 'Select Person', :name=>'project[user_ids][]' %>
by
<%= select_tag :projectmember, options_for_select(User.all.collect {|u| [u.lastname, u.id]}),:multiple => true, :prompt => 'Select Person', :name=>'project[projectmember][]' %>
and in my controller:
def create
#project = Project.new(params[:project])
users = User.find(params[:project][:projectmember]) rescue []
#project.users = users
respond_to do |format|
if #project.save
format.html { redirect_to #project, notice: 'Project was successfully created.' }
format.json { render json: #project, status: :created, location: #project }
#user_project=UserProject.create(:project_id => #project.id, :user_id => #project.projectmember)
#user_project=UserProject.create(:project_id => #project.id, :user_id => #project.projectheader)
i got now after creation :
#p=Project.all
Project id: 69, projectname: "test", projectdescription: "blabla", colourcode: "blue", projectheader: "5", projectmember: "---\n- '5'\n- '6'\n", projecttypename: "caucasian">]
#up=UserProject.all
UserProject id: 86, project_id: 69, user_id: 5, created_at: "2012-06-07 13:04:51", updated_at: "2012-06-07 13:04:51">
UserProject id: 87, project_id: 69, user_id: 6, created_at: "2012-06-07 13:04:51", updated_at: "2012-06-07 13:04:51">,
which i am happy about :)
still need to :
delete automatically the project/user couple if the project is deleted
show on the screen the corresponding member names rather than an id number...