Replace nil values with empty strings

README.md

@@ -137,6 +137,7 @@ Rabl.configure do |config|
   # config.xml_options = { :dasherize  => true, :skip_types => false }
   # config.view_paths = []
   # config.raise_on_missing_attribute = true # Defaults to false
+  # config.replace_nil_values_with_empty_strings = true # Defaults to false
 end
 ```
 
@@ -171,6 +172,8 @@ attempts to render an attribute that does not exist. Otherwise, the attribute wi
 Setting this to true during development may help increase the robustness of your code, but using `true` in
 production code is not recommended.
 
+If `replace_nil_values_with_empty_strings` is set to `true`, all values that are `nil` and would normally be displayed as `null` in the response are converted to empty strings.
+
 If you wish to use [oj](https://github.com/ohler55/oj) as
 the primary JSON encoding engine simply add that to your Gemfile:
 

lib/rabl/builder.rb

@@ -57,6 +57,14 @@ def compile_hash(options={})
         @_root_name = nil
       end
 
+      # Replace nil values with empty strings if configured
+      if Rabl.configuration.replace_nil_values_with_empty_strings
+        @_result = @_result.inject({}) do |hash, (k, v)|
+          hash[k] = v.nil? ? '' : v
+          hash
+        end
+      end
+
       # Return Results
       @_root_name ? { @_root_name => @_result } : @_result
     end

lib/rabl/configuration.rb

@@ -47,30 +47,32 @@ class Configuration
     attr_accessor :cache_engine
     attr_accessor :raise_on_missing_attribute
     attr_accessor :perform_caching
+    attr_accessor :replace_nil_values_with_empty_strings
 
     DEFAULT_XML_OPTIONS = { :dasherize  => true, :skip_types => false }
 
     def initialize
-      @include_json_root     = true
-      @include_child_root    = true
-      @include_msgpack_root  = true
-      @include_plist_root    = true
-      @include_xml_root      = false
-      @include_bson_root     = true
-      @enable_json_callbacks = false
-      @bson_check_keys       = false
-      @bson_move_id          = false
-      @json_engine           = nil
-      @msgpack_engine        = nil
-      @bson_engine           = nil
-      @plist_engine          = nil
-      @xml_options           = {}
-      @cache_sources         = false
-      @cache_all_output      = false
-      @escape_all_output     = false
-      @view_paths            = []
-      @cache_engine          = Rabl::CacheEngine.new
-      @perform_caching       = false
+      @include_json_root                     = true
+      @include_child_root                    = true
+      @include_msgpack_root                  = true
+      @include_plist_root                    = true
+      @include_xml_root                      = false
+      @include_bson_root                     = true
+      @enable_json_callbacks                 = false
+      @bson_check_keys                       = false
+      @bson_move_id                          = false
+      @json_engine                           = nil
+      @msgpack_engine                        = nil
+      @bson_engine                           = nil
+      @plist_engine                          = nil
+      @xml_options                           = {}
+      @cache_sources                         = false
+      @cache_all_output                      = false
+      @escape_all_output                     = false
+      @view_paths                            = []
+      @cache_engine                          = Rabl::CacheEngine.new
+      @perform_caching                       = false
+      @replace_nil_values_with_empty_strings = false
     end
 
     # @return The JSON engine used to encode Rabl templates into JSON

test/builder_test.rb

@@ -42,6 +42,19 @@
         topic.build(User.new, :root => false)
       end.equivalent_to({ :name => "rabl" })
     end
+
+    context "when nil values are replaced with empty strings" do
+      setup do
+        Rabl.configuration.replace_nil_values_with_empty_strings = true
+        builder({ :attributes => { :name => {} } })
+      end
+      asserts "that an empty string is returned as the value" do
+        topic.build(User.new(:name => nil))
+      end.equivalent_to({ :name => "" })
+      teardown do
+        Rabl.configuration.replace_nil_values_with_empty_strings = false
+      end
+    end
   end
 
   context "#attribute" do

test/configuration_test.rb

@@ -13,6 +13,7 @@
     asserts(:view_paths).equals []
     asserts(:json_engine).equals { json_engine }
     asserts(:cache_engine).is_a?(Rabl::CacheEngine)
+    asserts(:replace_nil_values_with_empty_strings).equals false
   end
 
   context 'custom JSON engine configured as Symbol' do
@@ -44,4 +45,14 @@
 
     asserts(:raise_on_missing_attribute).equals true
   end # raise on missing
+
+  context 'replace nil values with empty strings' do
+    setup do
+      Rabl.configure do |c|
+        c.replace_nil_values_with_empty_strings = true
+      end
+    end
+
+    asserts(:replace_nil_values_with_empty_strings).equals true
+  end # replace nil values with empty strings
 end

test/models/user.rb

@@ -10,12 +10,10 @@ class User
     DEFAULT_HOBBIES  = ['Photography']
 
     def initialize(attributes={})
-      self.age     = attributes[:age]     || DEFAULT_AGE
-      self.city    = attributes[:city]    || DEFAULT_CITY
-      self.name    = attributes[:name]    || DEFAULT_NAME
-      self.first   = attributes[:first]   || DEFAULT_FIRST
-      self.float   = attributes[:float]   || DEFAULT_FLOAT
-      self.hobbies = (attributes[:hobbies] || DEFAULT_HOBBIES).map { |h| Hobby.new(h) }
+      %w(age city name first float hobbies).each do |attr|
+        self.send "#{attr}=", (attributes.has_key?(attr.to_sym) ? attributes[attr.to_sym] : self.class.const_get("DEFAULT_#{attr.upcase}"))
+      end
+      self.hobbies = self.hobbies.map { |h| Hobby.new(h) }
     end
   end