Wrap BatchLoader for GraphQL

README.md

@@ -264,7 +264,7 @@ To avoid this problem, all we have to do is to change the resolver to return `Ba
 PostType = GraphQL::ObjectType.define do
   name "Post"
   field :user, !UserType, resolve: ->(post, args, ctx) do
-    BatchLoader.for(post.user_id).batch do |user_ids, loader|
+    BatchLoader::GraphQL.for(post.user_id).batch do |user_ids, loader|
       User.where(id: user_ids).each { |user| loader.call(user.id, user) }
     end
   end

lib/batch_loader/graphql.rb

@@ -2,29 +2,25 @@
 
 class BatchLoader
   class GraphQL
-    class Wrapper
-      def initialize(batch_loader)
-        @batch_loader = batch_loader
-      end
+    def self.use(schema_definition)
+      schema_definition.lazy_resolve(BatchLoader::GraphQL, :sync)
+    end
 
-      def sync
-        @batch_loader.__sync
-      end
+    def self.for(item)
+      new(item)
     end
 
-    def self.use(schema_definition)
-      schema_definition.lazy_resolve(BatchLoader::GraphQL::Wrapper, :sync)
-      schema_definition.instrument(:field, self)
+    def initialize(item)
+      @batch_loader = BatchLoader.for(item)
     end
 
-    def self.instrument(type, field)
-      old_resolve_proc = field.resolve_proc
-      new_resolve_proc = ->(object, arguments, context) do
-        result = old_resolve_proc.call(object, arguments, context)
-        result.respond_to?(:__sync) ? BatchLoader::GraphQL::Wrapper.new(result) : result
-      end
+    def batch(*args, &block)
+      @batch_loader.batch(*args, &block)
+      self
+    end
 
-      field.redefine { resolve(new_resolve_proc) }
+    def sync
+      @batch_loader.__sync
     end
   end
 end

spec/fixtures/graphql_schema.rb

@@ -7,10 +7,9 @@
 
   PostType = GraphQL::ObjectType.define do
     name "Post"
-    field :user, !UserType, resolve: ->(object, args, ctx) { object.user_lazy }
-    field :userId, !types.Int, resolve: ->(object, args, ctx) do
-      BatchLoader.for(object).batch do |posts, loader|
-        posts.each { |p| loader.call(p, p.user_lazy.id) }
+    field :user, !UserType, resolve: ->(object, args, ctx) do
+      BatchLoader::GraphQL.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
       end
     end
   end
@@ -31,15 +30,10 @@ class UserType < GraphQL::Schema::Object
 
   class PostType < GraphQL::Schema::Object
     field :user, UserType, null: false
-    field :user_id, Int, null: false
 
     def user
-      object.user_lazy
-    end
-
-    def user_id
-      BatchLoader.for(object).batch do |posts, loader|
-        posts.each { |p| loader.call(p, p.user_lazy.id) }
+      BatchLoader::GraphQL.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
       end
     end
   end

spec/graphql_spec.rb

@@ -10,7 +10,6 @@
       {
         posts {
           user { id }
-          userId
         }
       }
     QUERY
@@ -21,8 +20,8 @@
 
     expect(result['data']).to eq({
       'posts' => [
-        {'user' => {'id' => "1"}, "userId" => 1},
-        {'user' => {'id' => "2"}, "userId" => 2}
+        {'user' => {'id' => "1"}},
+        {'user' => {'id' => "2"}}
       ]
     })
   end