Allow custom formatters to be set with API settings.

CHANGELOG.markdown

@@ -3,7 +3,8 @@
 
 * [#265](https://github.com/intridea/grape/issues/264): Fix: Moved `ValidationError` into `Grape::Exceptions` - [@thepumpkin1979](https://github.com/thepumpkin1979).
 * [#269](https://github.com/intridea/grape/pull/269): Fix: `LocalJumpError` will not be raised when using explict return in API methods - [@simulacre](https://github.com/simulacre).
-* [#86] (https://github.com/intridea/grape/issues/275): Fix Path-based versioning not recognizing '/' route - [@walski](https://github.com/walski).
+* [#86](https://github.com/intridea/grape/issues/275): Fix Path-based versioning not recognizing '/' route - [@walski](https://github.com/walski).
+* [#277](https://github.com/intridea/grape/pull/277): Added a DSL to declare `formatter` in API settings - [@tim-vandecasteele](https://github.com/tim-vandecasteele).
 * Your contribution here.
 
 0.2.2

README.markdown

@@ -589,9 +589,12 @@ Serialization takes place automatically.
 Your API can declare additional types to support. Response format is determined by the
 request's extension, an explicit `format` parameter in the query string, or `Accept` header.
 
+Custom formatters for additional types can be defined with a proc or by method pointer.
+
 ``` ruby
 class Twitter::API < Grape::API
   content_type :xls, "application/vnd.ms-excel"
+  formatter :xls, lambda { |object| object.to_fancy_xls }
 end
 ```
 

lib/grape/api.rb

@@ -130,6 +130,10 @@ def format(new_format = nil)
         new_format ? set(:format, new_format.to_sym) : settings[:format]
       end
 
+      def formatter(content_type, new_formatter)
+        settings.imbue(:formatters, content_type.to_sym => new_formatter)
+      end
+
       # Specify the format for error messages.
       # May be `:json` or `:txt` (default).
       def error_format(new_format = nil)

lib/grape/endpoint.rb

@@ -395,7 +395,8 @@ def build_middleware
       b.use Grape::Middleware::Formatter,
         :format => settings[:format],
         :default_format => settings[:default_format] || :txt,
-        :content_types => settings[:content_types]
+        :content_types => settings[:content_types],
+        :formatters => settings[:formatters]
 
       aggregate_setting(:middleware).each do |m|
         m = m.dup

spec/grape/api_spec.rb

@@ -946,6 +946,26 @@ class CommunicationError < RuntimeError; end
     end
   end
 
+  describe ".formatter" do
+    context "multiple formatters" do
+      before :each do
+        subject.formatter :json, lambda { |object| "{\"custom_formatter\":\"#{object[:some]}\"}" }
+        subject.formatter :txt, lambda { |object| "custom_formatter: #{object[:some]}" }
+        subject.get :simple do
+          {:some => 'hash'}
+        end
+      end
+      it 'sets one formatter' do
+        get '/simple.json'
+        last_response.body.should eql '{"custom_formatter":"hash"}'
+      end
+      it 'sets another formatter' do
+        get '/simple.txt'
+        last_response.body.should eql 'custom_formatter: hash'
+      end
+    end
+  end
+
   describe ".default_error_status" do
     it 'should allow setting default_error_status' do
       subject.rescue_from :all