Question

I am working with DataMapper and Sinatra to create a simple app. Here’s the structure:

The app has Accounts. Each account has users and campaigns. Each user has comments that should be related to a specific campaign.

Comments should ideally have a user_id and a campaign_id to relate them both.

How can I relate the 2 together? Here’s the code that I have which does not work:

class Account
  include DataMapper::Resource
  property :id, Serial
  property :mc_username, String, :required => true
  property :mc_user_id, String, :required => true
  property :mc_api_key, String, :required => true
  property :created_at, DateTime
  property :updated_at, DateTime
  has n, :users
  has n, :campaigns
end

class User
  include DataMapper::Resource
  property :id, Serial
  property :name, String, :required => true
  property :email, String, :required => true
  property :is_organizer, Integer
  property :created_at, DateTime
  property :updated_at, DateTime
  belongs_to :account, :key => true
  has n, :comments
end

class Campaign
  include DataMapper::Resource
  belongs_to :mailchimpaccount, :key => true
  has n, :comments
  property :id, Serial
  property :cid, String
  property :name, String
  property :current_revision, Integer
  property :share_url, Text, :required => true
  property :password, String
  property :created_at, DateTime
  property :updated_at, DateTime
end

class Comment
  include DataMapper::Resource
  belongs_to :campaign, :key => true
  belongs_to :user, :key => true
  property :id, Serial
  property :at_revision, Integer
  property :content, Text
  property :created_at, DateTime
end

With this code, I can’t save a comment since I can’t figure out how to associate it to a campaign and a user at the same time. I can’t really get my head around wether I should even try to relate them at all using DataMapper.

I would love to know if this code is correct, how I can go about creating a comment that is related to both. If not, what structure and associations would be optimal for this scenario?

Thanks so much for the help!

Answer 1

So it seems that my thinking was correct. I can relate a comment to both a user and a campaign in this way:

# Get a user and a campaign first that we can relate to the comment
user = User.get(user_id)
campaign = Campaign.get(campaign_id)
comment = Comment.new
comment.content = "The comment's content"
user.comments << comment # This relates the comment to a specific user
campaign.comments << comment # This now relates the comment to a specific campaign
comment.save # Save the comment

Dangermouse’s suggestion to replace the :key => true option with :required => true also helped clean up the schema. Thanks!