association_without_primary_key.md

不通过主键(id)进行关联

相关文章

ActiveRecord关联的命名约定/规范

# 出现N+1查询问题的代码
markets.includes(:currency).map{ |market|
  market_type: Currency.find_by_code(ask_unit).coin_region
}

问题重现

markets表没有一个外键是currencies表的外键，好在belongs_to有选项可以指向非id列的关联

或者说ActiveRecord不管你的表结构如何，你想要指定哪一列是"主键"去关联都行

models/market.rb

belongs_to :currency, foreign_key: :ask_unit, primary_key: :code

usage.rb

markets.includes(:currency).map

参考链接

• https://stackoverflow.com/questions/16071735/active-record-association-without-using-id
• https://stackoverflow.com/questions/21466726/rails-has-many-relationship-without-using-id