problems getting ActiveMerchant PayPal Gateway to work on rails 3

I am trying to get PayPal 开发者_JAVA技巧Gateway to work on a rails 3 app. But I keep hitting this error "uninitialized constant ActiveMerchant::Billing::PayPalGateway (NameError)"

I've this in my development.rb:

ActiveMerchant::Billing::Base.mode = :test

::GATEWAY = ActiveMerchant::Billing::PayPalGateway.new(

:login => "API USERNAME ",

:password => "API PASSWORD",

:signature => "API SIGNATURE"

)

Please help!

Your capitalisation is wrong. Try:

ActiveMerchant::Billing::PaypalGateway