Q: How can we set Config parameters in spree I am new to Ruby on Rails. I am building one e-commerce application using Spree .Can anyone tell me where all the config parameters are defined?
 for instance most of models and controllers use Spree::Config[:currency].I want to know where this parameter is actually defined?

A: Take a look at:
https://github.com/spree/spree/blob/v3.0.1/core/app/models/spree/app_configuration.rb
and related classes like:
https://github.com/spree/spree/blob/v3.0.1/core/app/models/spree/preferences/configuration.rb
