Rails - Mar 2012 - Can I conditionaly initializer ?

Hello, I''m trying to add to spree functionlity
gateway of china, I check out the documentation and
follow the spree_gateway, in engine.rb

initializer "spree.gateway.payment_methods", :after =>
"spree.register.payment_methods" do |app|
        app.config.spree.payment_methods <<
Spree::Gateway::AuthorizeNetCim
        app.config.spree.payment_methods << Spree::Gateway::AuthorizeNet
        app.config.spree.payment_methods << Spree::Gateway::Eway
        app.config.spree.payment_methods << Spree::Gateway::Linkpoint
        app.config.spree.payment_methods << Spree::Gateway::PayPal
        app.config.spree.payment_methods << Spree::Gateway::SagePay
        app.config.spree.payment_methods << Spree::Gateway::Beanstream
        app.config.spree.payment_methods << Spree::Gateway::Braintree
        app.config.spree.payment_methods << Spree::Gateway::Stripe
        app.config.spree.payment_methods << Spree::Gateway::Samurai
end

so my,

initializer "spree.gateway.payment_methods_china", :after => "
spree.gateway.payment_methods" do |app|
        app.config.spree.payment_methods << Spree::Gateway::Alipay
end

I hope to write my gem more general,
so when spree_gateway exists
I initializer "spree.gateway.payment_methods_china", :after =>
"
spree.gateway.payment_methods"
when spree_gateway doesn''t exist,
I initializer "spree.gateway.payment_methods_china", :after =>
"
spree.register.payment_methods"

is it possible for rails engine to some kind conditionally say whether
a initializer
block exists?
(of course it doesn''t matter in my case, my payment gateway registers
before spree_gateway is also ok,
but is it possible to have this flexibility?
Thanks.

-- 
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http://www.aisiming.com/

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