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[英]Rails: How to create a has_many through association with an alias/class_name
[英]Rails custom ActiveRecord::Type fails when using `class_name` in has_many :through association
我在 Rails 應用程序中使用KSUID作為 UUID 的替代品。 michaelherold/ksuid-ruby將 KSUID 移植到 Ruby 並將它們實現為::ActiveRecord::Type::String
。 除了使用has_many :through associations
時的一個小錯誤has_many :through associations
與class_name
結合的has_many :through associations
時,一切都很好。
我能夠創建兩個 rspec 測試來演示該錯誤。
# code excerpt from link above
class Patient < ActiveRecord::Base
act_as_ksuid :id
has_many :appointments
has_many :physicians, through: :appointments
end
bundle exec rspec ./spec/cast1_spec.rb # works as expected, tests pass
當我更新患者的約會關聯以使用class_name
它會導致TypeError: can't cast KSUID::Type
。
# code excerpt from link above
class Patient < ActiveRecord::Base
act_as_ksuid :id
has_many :foobar, class_name: "Appointment" # <---- using class_name here
has_many :physicians, through: :foobar
end
bundle exec rspec ./spec/cast2_spec.rb # test fails
TypeError:
can't cast KSUID::Type
# ./spec/cast2_spec.rb:59:in `block (2 levels) in <top (required)>'
你能幫我找出問題並修復測試嗎? 要重現自己,請運行:
git clone https://github.com/mattes/ksuid-ruby.git
cd ksuid-ruby
git checkout cast_error
bundle install
bundle exec rspec ./spec/cast1_spec.rb # works
bundle exec rspec ./spec/cast2_spec.rb # fails
這看起來像一個 Rails 錯誤。
當解析一個through
關聯 ( patient.physicians
) 時,rails 會尋找一個與連接表名稱相同的關系,並且由於沒有 - 回退到字符串類型轉換(=不需要類型轉換,因此是錯誤)。
使示例工作的一個技巧是添加關系:
class Physician < ActiveRecord::Base
act_as_ksuid :id
has_many :foobar, class_name: "Appointment"
has_many :patients, through: :foobar
has_many :appointments # <= this is not used in app, but rails now can correctly resolve types
end
Rails master (6.1-alpha) 合並了pull request 36847 ,修復了一些情況,並輸出了一個更容易理解的錯誤:
NotImplementedError:為了正確鍵入 cast Patient.id,Physician 需要定義一個 :appointments 關聯。
但它似乎打破了其他一些情況,因此不確定 6.1 版本中會出現什么。 所以現在上面的 hack 或帶有 rails 版本保護的猴子補丁看起來是一個可行的解決方案。
附注。 無論實際適配器是什么,您的ksuid/activerecord/schema_statements
向PostgreSQLAdapter
添加類型。
聚苯乙烯。 您可以使用bundler/inline
和minitest/autorun
來創建一個自包含的示例(只需ruby filename.rb
運行):
require 'bundler/inline'
gemfile(ENV['INSTALL']=='1') do
source 'https://rubygems.org'
gem 'activerecord', '~>6.0.2' # also tested '~>5.2', '5.0' with same result, master with different error
gem 'sqlite3' # use , '~> 1.3.6' # for rails 5
gem 'ksuid', github: 'mattes/ksuid-ruby', ref:'e545b1b251bd6430c454509475963a7845b1da0f'
gem 'minitest'
end
require "active_record"
require "logger"
require "ksuid/activerecord"
require "ksuid/activerecord/table_definition"
# require "rails"
# require "ksuid/activerecord/schema_statements" # commented out to not load rails only to check Rails.env, instead:
require "active_record/connection_adapters/sqlite3_adapter"
::ActiveRecord::ConnectionAdapters::SQLite3Adapter::NATIVE_DATABASE_TYPES[:ksuid] = { name: "varchar", limit: 27 }
# require "ksuid/activerecord/quoting" # monkey-patch that fixes the error
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(IO::NULL)
ActiveRecord::Schema.verbose = false
ActiveRecord::Schema.define do
create_table(:physicians, force: true, id: :ksuid)
create_table(:patients, force: true, id: :ksuid)
create_table(:appointments, force: true, id: :ksuid) {|t| t.ksuid :physician_id, :patient_id }
end
class Physician < ActiveRecord::Base
act_as_ksuid :id
has_many :foobar, class_name: "Appointment"
has_many :patients, through: :foobar
has_many :appointments # the hack
end
class Appointment < ActiveRecord::Base
act_as_ksuids :id, :physician_id, :patient_id
belongs_to :physician
belongs_to :patient
end
class Patient < ActiveRecord::Base
act_as_ksuid :id
has_many :appointments
has_many :physicians, through: :appointments
end
ActiveSupport.run_load_hooks(:active_record, ActiveRecord::Base)
require "minitest/autorun"
describe "ActiveRecord integration" do
it "loads all associations correctly" do
patient = Patient.create!
physician = Physician.create!
appointment = Appointment.create!(patient_id: patient.id, physician_id: physician.id)
expect(patient.id.class).must_equal KSUID::Type
expect(patient.physicians.first).must_equal physician
expect(physician.patients.first).must_equal patient
end
end
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