ActiveModelSerializers::Model successor initialized with string keys fix (#1881)

Author: yevhene

CHANGELOG.md

@@ -12,6 +12,7 @@ Features:
 Fixes:
 
 - [#1833](https://github.com/rails-api/active_model_serializers/pull/1833) Remove relationship links if they are null (@groyoh)
+- [#1881](https://github.com/rails-api/active_model_serializers/pull/1881) ActiveModelSerializers::Model correctly works with string keys (@yevhene)
 
 Misc:
 

lib/active_model_serializers/model.rb

@@ -9,7 +9,7 @@ class Model
     attr_reader :attributes, :errors
 
     def initialize(attributes = {})
-      @attributes = attributes
+      @attributes = attributes && attributes.symbolize_keys
       @errors = ActiveModel::Errors.new(self)
       super
     end

test/active_model_serializers/model_test.rb

@@ -7,5 +7,16 @@ class ModelTest < ActiveSupport::TestCase
     def setup
       @resource = ActiveModelSerializers::Model.new
     end
+
+    def test_initialization_with_string_keys
+      klass = Class.new(ActiveModelSerializers::Model) do
+        attr_accessor :key
+      end
+      value = 'value'
+
+      model_instance = klass.new('key' => value)
+
+      assert_equal model_instance.read_attribute_for_serialization(:key), value
+    end
   end
 end