如何在 rails 中制作 "Unique many to many self joint"？

Question

我已经阅读了多对多的自我关节。我的问题是我需要它是独一无二的。

# app/models/word.rb
class Word < ApplicationRecord
    has_and_belongs_to_many(:defined, 
    class_name: 'Word', 
    join_table: 'defined_definers', 
    association_foreign_key: 'defined_id', 
    foreign_key: 'definer_id')
  has_and_belongs_to_many(:definers, 
    class_name: 'Word', 
    join_table: 'defined_definers', 
    association_foreign_key: 'definer_id', 
    foreign_key: 'defined_id')
end

这应该引发错误或不被执行：

word.definers << word.defined.first

否则，我的应用程序中可能会出现更严重的无法检测到的错误。

Answer 1

为了避免重复，您需要在数据库 add_index :defined_definers, [:definer_id, :defined_id], unique: true 中添加一个唯一索引，或者将每个地方的代码更改为 word.definers << word.defined.first unless word.definers.include?(word.defined)

如何在 rails 中制作 "Unique many to many self joint"？

How to make a "Unique many to many self joint" in rails?

ruby

validation

ruby-on-rails

associations