Alias for column names in Rails

Question

In my database has column names such as 'delete' or 'listen-control' and so on. These cannot be changed, so I would like to alias the names so as to avoid problems in my application.

I found the following code but it is outdated (05 Aug 2005) and doesn't work with Rails 3:

module Legacy   def self.append_features(base)     super     base.extend(ClassMethods)   end   module ClassMethods     def alias_column(options)       options.each do |new_name, old_name|         self.send(:define_method, new_name) { self.send(old_name) }         self.send(:define_method, "#{new_name}=") { |value| self.send("#{old_name}=", value) }       end     end   end end  ActiveRecord::Base.class_eval do   include Legacy end 

How can I alias the column names? Is it possible?

Answer 1

Declare this in your model.

alias_attribute :new_column_name, :column_name_in_db 

Answer 2

Aliasing method names won't solve your problem. As I mentioned in my comment above, you can't have dashes in ruby method or variable names, because ruby will interpret them as a "minus". so:

object.listen-control 

will be interpreted by ruby as:

object.listen - control 

and will fail. The code snippet you found might be failing because of ruby 1.9, not rails 3. Ruby 1.9 doesn't let you call .send on protected or private methods anymore, like 1.8 used to.

That being said, I do understand there are times when old database column names don't look very nice, and you want to clean them up. Create a folder in your lib folder called "bellmyer". Then create a file called "create_alias.rb", and add this:

module Bellmyer   module CreateAlias     def self.included(base)       base.extend CreateAliasMethods     end      module CreateAliasMethods       def create_alias old_name, new_name         define_method new_name.to_s do           self.read_attribute old_name.to_s         end          define_method new_name.to_s + "=" do |value|           self.write_attribute old_name.to_s, value         end       end     end   end end 

Now in your model that needs aliasing, you can do this:

class User < ActiveRecord::Base   include Bellmyer::CreateAlias   create_alias 'name-this', 'name_this' end 

And it will alias properly. It's using the read_attribute and write_attribute methods of ActiveRecord to access those table columns without calling them as ruby methods.