ActiveResource::Base.prefix isn't reset correctly when ActiveResource::Base.site is reset.

If you need to set the values for ActiveResource.site with a URI that includes a path, ActiveResource::Base.prefix will be wrong.

Consider this example. If you have an active resource called MyActiveResource (e.g.: )

class MyActiveResource < ActiveResource::Base
end

Setting a site value, and then another site value will produce the wrong ActiveResource::Base.prefix value, if the site url has a path.

See this example:

MyActiveResource.site = "http://www.example.com/app1"
# => "http://www.example.com/app1"
 MyActiveResource.prefix
# => "/app1/"
MyActiveResource.site = "http://www.example.com/app2"
# "http://www.example.com/app2"

MyActiveResource.prefix
# "/app1/"  <---- BUG ----

MyActiveResource.site.path
# => "/app2"  <-- Prefix above is wrong despite new, correct value of MyActiveResource.site.path

As you can see, even though you set a new site with a different path, the prefix method is not updated with the new site.path value, whereas it should be.

At first glance, this looks like it's because the first ActiveRecord::Base#prefix= call overrides the original prefix method with a new method, that retains the old value. Why does the prefix= override the prefix method with a new method??

      # Sets the \prefix for a resource's nested URL (e.g., <tt>prefix/collectionname/1.xml</tt>).
      # Default value is <tt>site.path</tt>.
      def prefix=(value = '/')
        # Replace :placeholders with '#{embedded options[:lookups]}'
        prefix_call = value.gsub(/:\w+/) { |key| "\#{options[#{key}]}" }

        # Clear prefix parameters in case they have been cached
        @prefix_parameters = nil

        # Redefine the new methods.
        code = <<-end_code
          def prefix_source() "#{value}" end
          def prefix(options={}) "#{prefix_call}" end                                     # <--- ????
        end_code
        silence_warnings { instance_eval code, __FILE__, __LINE__ }
      rescue
        logger.error "Couldn't set prefix: #{$!}\n  #{code}"
        raise
      end