What is the best way to setup my tables and relationships for this use case?

Question

1)A user can have many causes and a cause can belong to many users.

2)A user can have many campaigns and campaigns can belong to many users. Campaigns belong to one cause.

I want to be able to assign causes or campaigns to a given user, individually. So a user can be assigned a specific campaign. OR a user could be assigned a cause and all of the campaigns of that cause should then be associated with a user.

Is that possible? And could I set it up so that the relationships could be simplified like so:

User.causes = all causes that belong to a user

User.campaigns = all campaigns that belong to user whether through a cause association or campaign association

Answer 1

I believe you should use the following:

class User < ActiveRecord::Base
   has_and_belongs_to_many :causes
   has_and_belongs_to_many :campaigns
end

class Cause < ActiveRecord::Base
   has_and_belongs_to_many :users
   has_many :campaigns
end

class Campaign < ActiveRecord::Base
   has_and_belongs_to_many :users
   belongs_to :cause
end

This way you can use

User.causes
User.campaigns

Cause.campaing
Cause.users

Campaign.users
Campaign.cause

You can read here about has_and_belongs_to_many relationship, here about has_one and here about belongs_to.

Let me know if this is what you want :]

Edit:

"I would still need User.campaigns to be campaigns from a user's causes or individual campaigns associated with a user"

You can have a method on users model that returns all campaigns. Something like this:

def all_campaigns
   self.campaigns + self.causes.collect{ |c| c.campaigns }
end