Add CacheCrispies::Base#transform_keys method

README.md

@@ -112,6 +112,28 @@ end
 
 Put serializer files in `app/serializers/`. For instance this file should be at `app/serializers/cereal_serializer.rb`.
 
+### Snakecase to lower camel case
+You can pass a method to `transform_keys` in a serializer which will transform the keys for each attribute unless a `from` attribute was specified for that attribute.
+The configuration for `transform_keys` can be inherited, and overridden in the serializers that inherit from another.
+```ruby
+# app/serializers/base_serializer.rb
+class BaseSerializer < CacheCrispies::Base
+  transform_keys lambda { |key| key.to_s.camelize(:lower) } 
+end
+
+# app/serializers/crispy_serializer.rb
+class CrispySerializer < BaseSerializer
+  serialize :id, :created_at
+end
+```
+This will format the keys for each attribute using the passed in lambda like so:
+```json
+{
+  "id": "123",
+  "createdAt": "somedate"
+}
+```
+
 ### In your Rails controller
 ```ruby
 class CerealsController

lib/cache_crispies/base.rb

@@ -178,6 +178,16 @@ def self.file_hashes
       ).uniq.sort
     end
 
+    # Sets a method or Proc to transform keys by
+    #
+    # @param proc [Proc] a Proc to execute on serializable keys
+    # @return [Proc] a Proc to execute on the keys
+    def self.transform_keys(proc = nil)
+      return @transform_keys ||= proc if proc.present? || @transform_keys.present?
+
+      self.superclass.transform_keys if self.superclass.respond_to?(:transform_keys)
+    end
+
     private
 
     def self.file_hash
@@ -226,13 +236,14 @@ def self.serialize(
     )
       attribute_names.flat_map do |attrib|
         attrib = attrib&.to_sym
+        key = attrib
         current_nesting = Array(@nesting).dup
         current_conditions = Array(@conditions).dup
 
         @attributes <<
           Attribute.new(
-            attrib,
-            from: from,
+            transform_key(attrib),
+            from: from || attrib,
             with: with,
             through: through,
             to: to,
@@ -250,5 +261,15 @@ def self.merge(attribute = nil, with: nil)
       serialize(nil, from: attribute, with: with)
     end
     private_class_method :merge
+
+    # Transforms an attribute key using a specified Proc
+    #
+    # @param key [String] the key for an attribute
+    # @return [String] a transformed key
+    def self.transform_key(key)
+      return key if transform_keys.blank?
+
+      transform_keys.call(key)
+    end
   end
 end

spec/cache_crispies/base_spec.rb

@@ -39,6 +39,20 @@ def visible?
     end
   end
 
+  class BaseSerializer < CacheCrispies::Base
+    transform_keys lambda { |key| key.to_s.camelize(:lower) }
+  end
+
+  class InheritingSerializer < BaseSerializer
+    serialize :id, :snake_case
+  end
+
+  class OverriddenSerializer < BaseSerializer
+    transform_keys lambda { |key| key.to_s.upcase }
+
+    serialize :id, :snake_case
+  end
+
   let(:model) do
     OpenStruct.new(
       id: 42,
@@ -47,7 +61,8 @@ def visible?
       deeply_nested: true,
       nutrition_info: OpenStruct.new(calories: 1_000),
       organic: 'true',
-      legal: OpenStruct.new(parent_company: 'Disney probably')
+      legal: OpenStruct.new(parent_company: 'Disney probably'),
+      snake_case: 'i was snakecased'
     )
   end
 
@@ -95,6 +110,22 @@ def visible?
     end
   end
 
+  describe '.transform_keys' do
+    let(:serializer) { InheritingSerializer }
+
+    it 'transforms attribute keys' do
+      expect(subject.as_json.keys).to eq(%w[id snakeCase])
+    end
+
+    describe 'overridden serializers' do
+      let(:serializer) { OverriddenSerializer }
+
+      it 'transforms attribute keys' do
+        expect(subject.as_json.keys).to eq(%w[ID SNAKE_CASE])
+      end
+    end
+  end
+
   describe '.key' do
     it 'underscores the demodulized class name by default' do
       expect(serializer.key).to eq :cache_crispies_test