"Loại lỗi: không chuyển đổi ẩn nil thành chuỗi" khi mong muốn tải kết quả

Question

Tôi đang sử dụng ruby '2.3.0' và 'rails', '3.2.22.2'.

Tôi cần một chút trợ giúp & giải thích về truy vấn tôi đã thực hiện. Dưới đây là mô hình của tôi:

class AssessmentRaw < ActiveRecord::Base 
    belongs_to :session 
    has_many :schedulers, :class_name => 'MailingScheduler', :as => :owner, :dependent => :destroy 
end 

class MailingScheduler < ActiveRecord::Base 
    belongs_to :owner, :polymorphic => true 
end 

class Session < ActiveRecord::Base 
    has_many :assessment_raws, :dependent => :destroy 
end 

Tôi muốn lấy tất cả các assessment_raws, và tải háo hức phiên liên quan và mailing_schedulers.

chỉ

1. háo hức tải phiên

ars = AssessmentRaw.includes(:session).where("sessions.start_at >= ?", 1.year.ago).limit(10)

ars.map { |ar| ar.session.id } => [2877, 2878, 2879, 2880, 2881, 2882, 2883, 2884, 2902, 2903]

`ars.map { |ar| ar.schedulers.try(:size) }` 
    MailingScheduler Load (0.6ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 622 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.6ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 725 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.3ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 771 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.3ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 782 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.3ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 881 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.2ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 996 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.3ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 1087 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.3ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 1155 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.2ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 653 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
    MailingScheduler Load (0.2ms) SELECT "mailing_schedulers".* FROM "mailing_schedulers" WHERE "mailing_schedulers"."owner_id" = 940 AND "mailing_schedulers"."owner_type" = 'AssessmentRaw' 
=> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0] 

Tất nhiên để có được số lượng các mailing_schedulers, đường ray phải truy vấn (N + 1 vấn đề)

2. phiên tải háo hức và mailing_schedulers

ars = AssessmentRaw.includes(:schedulers,:session).where("sessions.start_at >= ?", 1.year.ago).limit(10)

TypeError: no implicit conversion of nil into String 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/arel-3.0.3/lib/arel.rb:40:in `initialize' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/arel-3.0.3/lib/arel.rb:40:in `new' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/arel-3.0.3/lib/arel.rb:40:in `sql' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_helper.rb:47:in `block in sanitize' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_helper.rb:45:in `map' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_helper.rb:45:in `sanitize' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_dependency/join_association.rb:104:in `block in join_to' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_dependency/join_association.rb:74:in `each' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_dependency/join_association.rb:74:in `each_with_index' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/associations/join_dependency/join_association.rb:74:in `join_to' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/query_methods.rb:370:in `block in build_joins' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/query_methods.rb:369:in `each' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/query_methods.rb:369:in `build_joins' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/query_methods.rb:266:in `build_arel' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/query_methods.rb:260:in `arel' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/finder_methods.rb:259:in `construct_limited_ids_condition' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/finder_methods.rb:243:in `apply_join_dependency' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/finder_methods.rb:232:in `construct_relation_for_association_find' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation/finder_methods.rb:211:in `find_with_associations' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation.rb:171:in `exec_queries' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation.rb:160:in `block in to_a' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/explain.rb:41:in `logging_query_plan' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation.rb:159:in `to_a' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/activerecord-3.2.22.2/lib/active_record/relation.rb:498:in `inspect' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/railties-3.2.22.2/lib/rails/commands/console.rb:47:in `start' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/railties-3.2.22.2/lib/rails/commands/console.rb:8:in `start' 
    from /Users/oim/.rbenv/versions/2.3.0/gemsets/project-gems/gems/railties-3.2.22.2/lib/rails/commands.rb:41:in `<top (required)>' 
    from script/rails:6:in `require' 
    from script/rails:6:in `<main>'irb(main):064:0> 

ouch. Tôi nghĩ rằng tôi cần một LEFT OUTER JOIN ở đây vì tất cả assessment_raws không có mailing_schedulers, đúng không?

Bất kỳ trợ giúp nào được đánh giá cao.

Answer 1

Sự cố này xảy ra do thay đổi được thực hiện trong Ruby 2.3, tại đó Hash giờ phản hồi lại to_proc gây nhầm lẫn với phương thức interpolate. Xem báo cáo lỗi này để biết thêm chi tiết: https://github.com/rails/rails/issues/25010. Cũng lưu ý có một giải pháp được đề cập đã giải quyết vấn đề cho tôi, nhưng trừ khi bạn chắc chắn rằng bạn không sử dụng to_proc mới, nó có khả năng có thể nguy hiểm.

gì làm việc cho tôi: tôi đã thêm các bản vá khỉ gợi ý (như hình dưới đây) để đầu config/application.rb

class Hash 
    undef_method :to_proc if self.method_defined?(:to_proc) 
end