Require concurrent/ruby when concurrent_write changes

lib/cached_resource/cached_resource.rb

@@ -19,14 +19,15 @@ def cached_resource(options={})
         def setup_cached_resource!(options)
           @cached_resource = CachedResource::Configuration.new(options)
           if @cached_resource.concurrent_write
-            begin
-              send :require, 'concurrent/promise'
-            rescue LoadError
-              @cached_resource.logger.error(
-                "`concurrent_write` option is enabled, but `concurrent-ruby` is not an installed dependency"
-              )
-              raise
-            end
+            @cached_resource.require_concurrent_ruby
+            # begin
+            #   send :require, 'concurrent/promise'
+            # rescue LoadError
+            #   @cached_resource.logger.error(
+            #     "`concurrent_write` option is enabled, but `concurrent-ruby` is not an installed dependency"
+            #   )
+            #   raise
+            # end
           end
           send :include, CachedResource::Caching
           @cached_resource

lib/cached_resource/configuration.rb

@@ -59,6 +59,25 @@ def off!
       self.enabled = false
     end
 
+    def concurrent_write=(value)
+      super(value)
+
+      if value
+        self.require_concurrent_ruby
+      end
+    end
+
+    def require_concurrent_ruby
+      begin
+        send :require, 'concurrent/promise'
+      rescue LoadError
+        @cached_resource.logger.error(
+          "`concurrent_write` option is enabled, but `concurrent-ruby` is not an installed dependency"
+        )
+        raise
+      end
+    end
+
     private
 
     # Get a randomized ttl value between ttl * ttl_randomization_scale begin

spec/spec_helper.rb

@@ -3,7 +3,7 @@
 require 'active_resource'
 require 'active_support'
 require 'active_support/time'
-require 'concurrent/promise'
+# require 'concurrent/promise'
 
 $:.unshift(File.dirname(__FILE__) + '/../lib')
 require 'cached_resource'