Relational DB - Related and not Related

rubyonrails-talk
1

Hi

I’m working on a project that has users and groups, users can be members of a group or they can just be a user - what’s going to be the best way to deal with this? I understand the normal has_many relationship just not sure how to do this one. Will try to post some code snippets tomorrow.

Thanks, Cameron

2

has_many :through seems perfect for this, given the many-to-many nature and the possibility you'll want to have additional info about the relationship (like when they joined, positions held within the group, etc.).

-Dave

3

If the user can only be a member of one group then use User belongs_to group. If a particular member does not belong to a group then just leave group_id nil. You will obviously have to allow for user.group == nil in the code where appropriate. If he can belong to many (or no) groups then use has_many :through as Dave suggested. You can test user.groups to see if he is in any groups.

4

Oh, good point. I was assuming (and you know what happens then!) that a User could belong to many Groups.

-Dave

5

Thanks Dave & Colin! That was how I had hoped it would work!

6

Here is an update, I have it working as only a group or as only a non-group user. I have below the create controller and was wondering what would be the best way to allow associations and non-associated records. Thanks

def create

if Group.nil?

@group = Group.find(params[:group_id])

@user = @group.users.create(params[:user])

else

@user = User.new

@user.ip_address = request.remote_ip

@user.ua_string = request.user_agent

@user = User.new(params[:user])

end

respond_to do |format|

if @user.save && @user.group_id == nil

format.html { redirect_to “/”, notice: ‘Thank you for registering!’ }

elsif @user.save && @user.group_id != “”

format.html { redirect_to group_path(@group.token), notice: ‘Thank you for registering!’ }

else

format.html { render action: “new” }

format.json { render json: @user.errors, status: :unprocessable_entity }

end

end

end

7

This will do (or at least try) the save twice, if the user has a group. I'd recommend:

if it saves   redirect to (if it has a group, the group, else /) else   give error msg end

Also, look closely at the way you're checking for a group. The first option will trigger if the group is nil, the second if it's not "" (empty string)... but what if it *is* ""? That's neither nil nor not-"", so it will take the "else" path and pretend like it didn't save. I suggest you use .blank? (or its inverse, .present?) to tell if it's there or not. Both nil and "" count as blank (and not present).

-Dave

8

Here is an update, I have it working as only a group or as only a non-group user. I have below the create controller and was wondering what would be the best way to allow associations and non-associated records. Thanks

  def create     if Group.nil?

Can you explain what the above line is for?

Colin