Error while installing gem in Ruby on Rails project - ruby-on-rails

Question

I created a simple web project in ROR - postgresql as a DB
C:\Sites\nested>ruby -v
ruby 1.9.3p484 (2013-11-22) [i386-mingw32]
C:\Sites\nested>rails -v
Rails 4.0.2
When I try to add an automatic foreign key either by command line
C:\Sites\nested>gem install automatic_foreign_key
or edit the gem file by adding
# create automatic foreign key
gem "automatic_foreign_key", "~> 1.3.0"
I got the following error when running the server
C:\Sites\nested>rails s
C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-4.0.2/lib/active_support/core_ext/module/aliasing.rb:32:in `alias_method': undefined method `to_sql' for class `ActiveRecord::ConnectionAdapters::Tab leDefinition' (NameError)
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-.0.2/lib/active_support/core_ext/module/aliasing.rb:32:in `alias_method_chain'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/redhillonrails_core-.2.0/lib/redhillonrails_core/active_record/connection_adapters/table_definition.rb:9:in `block in included'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/redhillonrails_core-.2.0/lib/redhillonrails_core/active_record/connection_adapters/table_definition.rb:6:in `class_eval'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/redhillonrails_core-.2.0/lib/redhillonrails_core/active_record/connection_adapters/table_definition.rb:6:in `included'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/redhillonrails_core-.2.0/lib/redhillonrails_core.rb:32:in `include'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/redhillonrails_core-.2.0/lib/redhillonrails_core.rb:32:in `<top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-.0.2/lib/active_support/dependencies.rb:229:in `require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-.0.2/lib/active_support/dependencies.rb:229:in `block in require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-.0.2/lib/active_support/dependencies.rb:214:in `load_dependency'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/activesupport-.0.2/lib/active_support/dependencies.rb:229:in `require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/automatic_foreign_key-.3.0/lib/automatic_foreign_key.rb:5:in `rescue in <top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/automatic_foreign_key-.3.0/lib/automatic_foreign_key.rb:1:in `<top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:72:in `require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:70:in `each'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:70:in `block in require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:59:in `each'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler/runtime.rb:59:in `require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/bundler-.3.5/lib/bundler.rb:132:in require'
from C:/Sites/nested/config/application.rb:7:in `<top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-.0.2/lib/rails/commands.rb:74:in `require'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-.0.2/lib/rails/commands.rb:74:in `block in <top (required)>'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-.0.2/lib/rails/commands.rb:71:in `tap'
from C:/RailsInstaller/Ruby1.9.3/lib/ruby/gems/1.9.1/gems/railties-.0.2/lib/rails/commands.rb:71:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'

Answer 1

FYI this is your error:
`alias_method': undefined method `to_sql' for class `ActiveRecord::ConnectionAdapters::Tab leDefinition' (NameError)
Looks like the gem is creating an alias_method for .to_sql. Alias method basicaly calls a method by another name, so you can use it in different contexts
We use alias_method :name, :title a lot, because we standardize our validations, meaning we need to keep the same method names each time
Error
The actual error is caused by your class not having the to_sql method. I've never encountered this, so I looked it up:
Seems the issue is caued by Rails 4. As for a solution, I would suggest that since automatic_foreign_key hasn't been updated since 2011, it's going to be incompatible with Rails 4
If we take that idea as the problem, maybe you could detail how you want it to work & we could create a work-around?

Answer 2

try this
C:\Sites\nested>gem install --local automatic_foreign_key
and also bundle install --local in your project terminal and then edit gem "automatic_foreign_key", "~> 1.3.0" in your gem file