Add .defined_schema method (#98)

Author: glaucocustodio

CHANGELOG.md

@@ -1,3 +1,8 @@
+# Next (unreleased)
+
+## Added
+* `.defined_schema` to return the schema that has been defined with `json_schema` ([@glaucocustodio][]) [#98](https://github.com/nesaulov/surrealist/pull/98)
+
 # 1.1.2
 
 ## Fixed
@@ -87,6 +92,7 @@
 * Allow nil values by default.
 * Allow nested objects.
 
+[@glaucocustodio]: https://github.com/glaucocustodio
 [@nesaulov]: https://github.com/nesaulov
 [@AlessandroMinali]: https://github.com/AlessandroMinali
 [@nulldef]: https://github.com/nulldef

README.md

@@ -27,6 +27,7 @@ to serialize nested objects and structures. [Introductory blogpost.](https://med
   * [Defining custom serializers](#defining-custom-serializers)
   * [Multiple serializers](#multiple-serializers)
   * [Build schema](#build-schema)
+  * [Defined schema](#defined-schema)
   * [Working with ORMs](#working-with-orms)
     * [ActiveRecord](#activerecord)
     * [ROM](#rom)
@@ -260,19 +261,19 @@ you have to define yourself. DSL looks as follows
 class IncomeSerializer < Surrealist::Serializer
   serializer_context :current_user
   json_schema { { amount: Integer } }
-  
+
   def amount
     current_user.guest? ? 100000000 : object.amount
   end
 end
-``` 
+```
 `.serializer_context` takes an array of symbols and dynamically defines instance methods
 that read values from the context hash. So `.serializer_context :current_user` will become
 ``` ruby
 def current_user
   context[:current_user]
 end
-``` 
+```
 There is also an alias in the plural form: `.serializer_contexts`.
 ### Multiple serializers
 
@@ -321,6 +322,14 @@ Car.new.build_schema
 # => { age: 7, brand: "Toyota", doors: nil, horsepower: 140, fuel_system: "Direct injection", previous_owner: "John Doe" }
 ```
 
+### Defined schema
+Use the `.defined_schema` method to get the schema that has been defined with `json_schema`:
+
+``` ruby
+User.defined_schema
+# => { name: String, age: Integer }
+```
+
 ### Working with ORMs
 
 There are two kinds of return values of ORM methods: some return collections of objects, while others return instances.

lib/surrealist/class_methods.rb

@@ -55,6 +55,28 @@ def json_schema(&_block)
       SchemaDefiner.call(self, yield)
     end
 
+    # A DSL method to return the defined schema.
+    # @example DSL usage example
+    #   class Person
+    #     include Surrealist
+    #
+    #     json_schema do
+    #       { name: String }
+    #     end
+    #
+    #     def name
+    #       'Parent'
+    #     end
+    #   end
+    #
+    #   Person.defined_schema
+    #   # => { name: String }
+    def defined_schema
+      read_schema.tap do |schema|
+        raise UnknownSchemaError if schema.nil?
+      end
+    end
+
     # A DSL method to delegate schema in a declarative style. Must reference a valid
     # class that includes Surrealist
     #
@@ -101,9 +123,17 @@ def delegate_surrealization_to(klass)
     def surrealize_with(klass, tag: Surrealist::VarsHelper::DEFAULT_TAG)
       if klass < Surrealist::Serializer
         Surrealist::VarsHelper.add_serializer(self, klass, tag: tag)
+        instance_variable_set(VarsHelper::PARENT_VARIABLE, klass.defined_schema)
       else
         raise ArgumentError, "#{klass} should be inherited from Surrealist::Serializer"
       end
     end
+
+    private
+
+    def read_schema
+      instance_variable_get(VarsHelper::INSTANCE_VARIABLE) ||
+        instance_variable_get(VarsHelper::PARENT_VARIABLE)
+    end
   end
 end

spec/schema_spec.rb

@@ -0,0 +1,61 @@
+class WithSchema
+  include Surrealist
+
+  json_schema { { name: String, age: Integer } }
+
+  def name
+    'John'
+  end
+
+  def age
+    21
+  end
+end
+
+class WithoutSchema
+  include Surrealist
+end
+
+class PersonSerializer < Surrealist::Serializer
+  json_schema { { age: Integer } }
+
+  def age
+    20
+  end
+end
+
+class WithCustomSerializer
+  include Surrealist
+  attr_reader :age
+
+  surrealize_with PersonSerializer
+
+  def initialize(age)
+    @age = age
+  end
+end
+
+RSpec.describe Surrealist do
+  describe '.defined_schema' do
+    context 'json schema defined' do
+      context 'using custom serializer' do
+        it 'returns the defined json_schema' do
+          expect(PersonSerializer.defined_schema).to eq(age: Integer)
+          expect(WithCustomSerializer.defined_schema).to eq(age: Integer)
+        end
+      end
+
+      context 'not using custom serializer' do
+        it 'returns the defined json_schema' do
+          expect(WithSchema.defined_schema).to eq(name: String, age: Integer)
+        end
+      end
+    end
+
+    context 'json schema not defined' do
+      it 'raises UnknownSchemaError' do
+        expect { WithoutSchema.defined_schema }.to raise_error(Surrealist::UnknownSchemaError)
+      end
+    end
+  end
+end