Getting data from an ancestor (I think)

rubyonrails-talk
1

I'm setting up a music catalogue to learn my way around RoR. In index.html.erb I would like to show the band name instead of the id. What is the proper way to do this?

# records.rb class Record < ActiveRecord::Base   belongs_to :band; end

# bands.rb class Band < ActiveRecord::Base   has_many :records end

# views/records/index.html.erb ... <% @records.each do |record| %>   <tr>     <td><%=h record.band.name %></td>     <td><%=h record.title %></td>     <td><%=h record.description %></td> ...

2

I'm setting up a music catalogue to learn my way around RoR. In index.html.erb I would like to show the band name instead of the id. What is the proper way to do this?

# records.rb

That should be record.rb, not records

class Record < ActiveRecord::Base belongs_to :band; end

# bands.rb

Again, should be singular

class Band < ActiveRecord::Base has_many :records end

# views/records/index.html.erb ... <% @records.each do |record| %> <tr> <td><%=h record.band.name %></td>

That should work, assuming you change the filenames above. Watch out for the case where no band has been allocated, however, ie record.band is nil

Colin

3

Which is one reason that I'd recommend not having the view reach through one model to get to the attributes of another, a violation of the "law" of demeter (which I personally call the "strong suggestion" of demeter.

So I'd do something like:

in the view

... <td><%=h record.artist %></td>

and in the record model

class Record < ActiveRecord::Base    belongs_to band

   def artist        if band           band.name        else           "Anonymous"        end    end end

This decouples the view from the DB representation, and will make changes down the road like changing the database schema to allow multiple artist compilations to be represented, when you will change the belongs_to and has_many relations in Record and Band to either has_and_belongs_to_many or has_many :through associations.