Improve model class of ruby-client (#1670)

* Add Model.build_from_hash

* Use Model.build_from_hash instead of Model.new.build_from_hash

* Update sample for ruby-client

* Update sample for openapi3 ruby-client

modules/openapi-generator/src/main/resources/ruby-client/api_client.mustache

@@ -204,9 +204,7 @@ module {{moduleName}}
         end
       else
         # models, e.g. Pet
-        {{moduleName}}.const_get(return_type).new.tap do |model|
-          model.build_from_hash data
-        end
+        {{moduleName}}.const_get(return_type).build_from_hash(data)
       end
     end
 

modules/openapi-generator/src/main/resources/ruby-client/base_object.mustache

@@ -1,3 +1,10 @@
+    # Builds the object from hash
+    # @param [Hash] attributes Model attributes in the form of hash
+    # @return [Object] Returns the model itself
+    def self.build_from_hash(attributes)
+      new.build_from_hash(attributes)
+    end
+
     # Builds the object from hash
     # @param [Hash] attributes Model attributes in the form of hash
     # @return [Object] Returns the model itself
@@ -58,8 +65,7 @@
           end
         end
       else # model
-        temp_model = {{moduleName}}.const_get(type).new
-        temp_model.build_from_hash(value)
+        {{moduleName}}.const_get(type).build_from_hash(value)
       end
     end
 

modules/openapi-generator/src/main/resources/ruby-client/partial_model_enum_class.mustache

@@ -2,6 +2,13 @@
     {{#allowableValues}}{{#enumVars}}
     {{{name}}} = {{{value}}}.freeze{{/enumVars}}{{/allowableValues}}
 
+    # Builds the enum from string
+    # @param [String] The enum value in the form of the string
+    # @return [String] The enum value
+    def self.build_from_hash(value)
+      new.build_from_hash(value)
+    end
+
     # Builds the enum from string
     # @param [String] The enum value in the form of the string
     # @return [String] The enum value
@@ -10,4 +17,4 @@
       raise "Invalid ENUM value #{value} for class #{{{classname}}}" if constantValues.empty?
       value
     end
-  end
+  end

modules/openapi-generator/src/main/resources/ruby-client/partial_model_generic.mustache

@@ -239,8 +239,7 @@
       {{#-first}}
       _any_of_found = false
       openapi_any_of.each do |_class|
-        _any_of = {{moduleName}}.const_get(_class).new
-        _any_of.build_from_hash(self.to_hash)
+        _any_of = {{moduleName}}.const_get(_class).build_from_hash(self.to_hash)
         if _any_of.valid?
           _any_of_found = true
         end
@@ -256,8 +255,7 @@
       {{#-first}}
       _one_of_found = false
       openapi_one_of.each do |_class|
-        _one_of = {{moduleName}}.const_get(_class).new
-        _one_of.build_from_hash(self.to_hash)
+        _one_of = {{moduleName}}.const_get(_class).build_from_hash(self.to_hash)
         if _one_of.valid?
           if _one_of_found?
             return false