How to use field resolver or extension for fields I want batched.

[jhirn]

Hello. I'm trying to figure out a way to write a custom field extension or resolver to use for basic cases when I want to batch load. In fact I'd love to automatically use this resolver/extension when the field is an ActiveRecord association, but one step at a time.

I've implemented Sources::Association with data loader and can use it like this:

module Types
  class CountyType < Types::BaseObject
    field :cbsa, Types::CbsaType, null: false
    
    # repetative, yuck 
    def cbsa
      dataloader.with(Sources::Association, :cbsa).load(object)
    end
  end
end

But what I'd like is

module Types
  class CountyType < Types::BaseObject

    field :cbsa, Types::CbsaType, null: false, resolver: Resolvers::Association

    ## or 

    field :cbsa, Types::CbsaType, null: false, extensions: [Extensions::BatchAssociation]

    ## Ultimately (if possible)

    field :cbsa, Types::CbsaType, null: false ## determine object.field is AR association and automatically batch
  end
end

I'm trying to wrap my head around how to do this but it seemed difficult enough to convince me it might not be a great idea. In my head it feels like implementing resolve in an Extension would be simple enough but I'm not exactly sure how to get the field name to symbolize to pass to data loader. Something like

class AssociationExtension < GraphQL::Schema::FieldExtension
  def resolve(object:, arguments:, **rest)
      # naive, ignores arguments, could be enhanced. 
      dataloader.with(Sources::Association, FIELD_NAME).load(object)
   end
end

I suppose I could initialize it with the field name but it's redundant and verbose.

 field :cbsa, Types::CbsaType, null: false, extensions: [Extensions::BatchAssociation => {field_name: :cbsa]

Not exactly sure how the custom resolver would work as I don't want to declare args/type/etc... in the Resolver. I just want the resolve method to use my dataloader source.

Anyways what are people's thoughts. Talk me out of this because it's spinning my wheels 🙃

[jhirn]

One possibility would be to use context.current_path.last.to_symto get field name in the resolver but I'm not quite familiar enough with context to know if that's always going to be the case.

class AssociationExtension < GraphQL::Schema::FieldExtension
  def resolve(object:, arguments:, **rest)
      context.current_path #=> ["counties", 0, "cbsa"]
      field_name =  context.current_path.last.to_sym  #=> :cbsa
      dataloader.with(Sources::Association, field_name).load(object)
   end
end

Going to try this later on and report back, but also waiting for someone to talk me out of this idea entirely.

[rmosolgo]

FieldExtensions have a reference to the field they're attached to, that might help:

graphql-ruby/lib/graphql/schema/field_extension.rb

Lines 12 to 13 in 930468f

	# @return [GraphQL::Schema::Field]
	attr_reader :field

But I think if it was me, I'd use a resolver, something like this:

class Types::BaseField < GraphQL::Schema::Field 
  class DataloadRelationResolver < GraphQL::Schema::Resolver 
    def resolve
      dataloader.with(Sources::Association, @field.original_name).load(object) 
    end 
  end 

  def initialize(*args, dataload_relation: false, **kwargs, &block)
    if dataload_relation 
      # TODO add a check to see if there's already a resolver, raise an ArgumentError if so
      kwargs[:resolver] = DataloadRelationResolver
    end 
    super(*args, **kwargs, &block)
  end 
end 

Then use it like:

field :cbsa, Types::CbsaType, dataload_relation: true 

I wouldn't recommend using context[:current_path] because it will include any field aliases in the query, for example:

{
  county(id: $id) {
    blah: cbsa { ... } 
    # ^^ in this case, context[:current_path] would have "blah" at the end
  }
}

[jhirn]

Very cool. I will give this a try.

…

On Thu, Jan 25, 2024 at 3:22 PM Robert Mosolgo ***@***.***> wrote: FieldExtensions have a reference to the field they're attached to, that might help: https://github.com/rmosolgo/graphql-ruby/blob/930468fb4d39a62a21baf341f0c98932a15c3ba9/lib/graphql/schema/field_extension.rb#L12-L13 But I think if it was me, I'd use a resolver, something like this: class Types::BaseField < GraphQL::Schema::Field class DataloadRelationResolver < GraphQL::Schema::Resolver def resolve dataloader.with(Sources::Association, @field.original_name).load(object) end end def initialize(*args, dataload_relation: false, **kwargs, &block) if dataload_relation # TODO add a check to see if there's already a resolver, raise an ArgumentError if so kwargs[:resolver] = DataloadRelationResolver end super(*args, **kwargs, &block) end end Then use it like: field :cbsa, Types::CbsaType, dataload_relation: true I wouldn't recommend using context[:current_path] because it will include any field aliases in the query, for example: { county(id: $id) { blah: cbsa { ... } # ^^ in this case, context[:current_path] would have "blah" at the end } } — Reply to this email directly, view it on GitHub <#4806 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AABIZMP37P53GZINUN6XVI3YQLEJRAVCNFSM6AAAAABCH5WFX6VHI2DSMVQWIX3LMV43SRDJONRXK43TNFXW4Q3PNVWWK3TUHM4DENJQGEYDE> . You are receiving this because you authored the thread.Message ID: ***@***.***>