ruby-acts-as-api - 1.0.1-2.1 main

It provides a simple interface to determine the representation of your
model data, that should be rendered in your API responses.
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In addition to Rails it theoretically can be used with any ruby app and
any database (__ActiveRecord__ and __Mongoid__ are supported out of the
box) as it only has few dependencies.
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The lib is _very_ fast in generating your responses and battle tested in
production with platforms like Diaspora or flinc.