66 lines
1.9 KiB
Ruby
66 lines
1.9 KiB
Ruby
# references:
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# https://github.com/Shopify/graphql-batch/blob/master/examples/association_loader.rb
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# https://gist.github.com/palkan/03eb5306a1a3e8addbe8df97a298a466
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# https://evilmartians.com/chronicles/active-storage-meets-graphql-pt-2-exposing-attachment-urls
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module Loaders
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class Association < GraphQL::Batch::Loader
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def self.validate(model, association_name)
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new(model, association_name)
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nil
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end
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def initialize(model, association_schema)
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@model = model
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@association_schema = association_schema
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@association_name = extract_association_id(association_schema)
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validate
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end
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def load(record)
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raise TypeError, "#{@model} loader can't load association for #{record.class}" unless record.is_a?(@model)
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return Promise.resolve(read_association(record)) if association_loaded?(record)
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super
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end
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# We want to load the associations on all records, even if they have the same id
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def cache_key(record)
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record.object_id
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end
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def perform(records)
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preload_association(records.uniq)
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records.each { |record| fulfill(record, read_association(record)) }
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end
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private
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def validate
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unless @model.reflect_on_association(@association_name)
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raise ArgumentError, "No association #{@association_name} on #{@model}"
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end
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end
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def preload_association(records)
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::ActiveRecord::Associations::Preloader.new.preload(records, @association_schema)
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end
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def read_association(record)
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record.public_send(@association_name)
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end
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def association_loaded?(record)
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record.association(@association_name).loaded?
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end
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def extract_association_id(id_or_hash)
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return id_or_hash unless id_or_hash.is_a?(Hash)
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if id_or_hash.keys.size != 1
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raise ArgumentError, "You can only preload exactly one association! You passed: #{id_or_hash}"
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end
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id_or_hash.keys.first
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end
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end
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end
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