Undefined method when running db:schema:dump using pg_power gem - postgresql

Question

I have a migration I am trying to run to generate postgresql schemas using pg_power.
class CreateSchemas < ActiveRecord::Migration
def change
create_schema 'deprecated'
create_schema 'leaf'
create_schema 'mmp'
create_schema 'mmp_static'
create_schema 'nass'
create_schema 'static'
end
end
When I run the migration, I get the following error
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Invoke db:load_config (first_time)
** Execute db:load_config
** Execute db:migrate
** Invoke db:_dump (first_time)
** Execute db:_dump
** Invoke db:schema:dump (first_time)
** Invoke environment
** Invoke db:load_config
** Execute db:schema:dump
rake aborted!
undefined method `[]' for nil:NilClass
/Users/Pro777/.bundler/ruby/2.0.0/pg_power-36a643247425/lib/pg_power/schema_dumper/extension_methods.rb:17:in `block in dump_extensions'
/Users/Pro777/.bundler/ruby/2.0.0/pg_power-36a643247425/lib/pg_power/schema_dumper/extension_methods.rb:15:in `map'
/Users/Pro777/.bundler/ruby/2.0.0/pg_power-36a643247425/lib/pg_power/schema_dumper/extension_methods.rb:15:in `dump_extensions'
/Users/Pro777/.bundler/ruby/2.0.0/pg_power-36a643247425/lib/pg_power/schema_dumper/extension_methods.rb:6:in `header_with_extensions'
/Library/Ruby/Gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/schema_dumper.rb:26:in `dump'
/Library/Ruby/Gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/schema_dumper.rb:21:in `dump'
/Library/Ruby/Gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:244:in `block (4 levels) in <top (required)>'
/Library/Ruby/Gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:243:in `open'
/Library/Ruby/Gems/2.0.0/gems/activerecord-4.0.0/lib/active_record/railties/databases.rake:243:in `block (3 levels) in <top (required)>'
I should say I'm using ruby 2.0, rails 4.0, and the rails4 branch of pg_power.

Answer 1

The library was tested with Ruby <= 1.9.3 (you are using 2.0) and ActiveRecord 3.
It was tested with Rails 3.1.x and 3.2.x, Ruby 1.8.7 REE and 1.9.3.
Moreover, there seems to be some incompatibilities with Rails 4.
The library doesn't use public ActiveRecord API but uses monkey patching (alias_method_chain). I won't be surprise if the exception is because the library does not currently work with Rails 4.
In order to fix the issue you should look what changed in the ActiveRecord internals from Rails 3 to Rails 4 and update the corresponding overrides in the Gem. It may be a small or huge effort, depending on the amount of changes.
I encourage you find an alternative and report the issue in the official issue tracker.

Answer 2

When you was trying to run pg_power against rails4, it really didn't work well.
Now, pg_power supports rails4, you must use 2.X.X version.