lib/quandl/api_config.rb in quandl-1.0.3 vs lib/quandl/api_config.rb in quandl-1.0.4

@@ -1,9 +1,11 @@
+# frozen_string_literal: true
+
 module Quandl
   class ApiConfig
-    API_KEY_THREAD_KEY = 'quandl_api_key'
-    API_BASE_THREAD_KEY = 'quandl_api_base'
-    API_VERSION_THREAD_KEY = 'quandl_api_version_key'
+    API_KEY_THREAD_KEY = 'quandl_api_key'.freeze
+    API_BASE_THREAD_KEY = 'quandl_api_base'.freeze
+    API_VERSION_THREAD_KEY = 'quandl_api_version_key'.freeze
 
     @api_key = nil
     @api_base = nil
     @api_version = nil