Work with Sinatra

[a2ikm]

To enable ActiveDecorator in Sinatra, register it like:

require "active_decorator/sinatra"
register ActiveDecorator::Sinatra

Then ActiveDecorator::Sinatra reads ROOT/decorators/*_decorator.rb,
and decorates instance variables in scope and local variables passed
via render method with them.

The ROOT/decorators directory is used by default. If you want to use
another directory, you can set it as :decorators like:

require "active_decorator/sinatra"
set :decorators, "/path/to/your/decorators"
register ActiveDecorator::Sinatra

ActiveDecorator::Sinatra doesn't decorate following instance variables
by default:

@default_layout @env @params @preferred_extension
@request @response @template_cache

These are declared in an array named as
ActiveDecorator::Sinatra::DEFAULT_PROTECTED_INSTANCE_VARIABLES. If you
want to protect other instance variables, you can declare them as
:protected_instance_variables like:

require "active_decorator/sinatra"
set :protected_instance_variables, %w[@foo @bar]
register ActiveDecorator::Sinatra

Note that these set statements must be placed before the register
statement.

Specs for Sinatra run with the fllowing command:

`BUNDLER_GEMFILE=gemfiles/Gemfile-sinatra bundle exec rake spec:sinatra`

Sinatra doesn't support implicit object rendering (like render @author),
so features about this won't tested in the partial spec. This switching
is made with rails? method decrared in spec_helper.rb.