如何按属性确定多态关联的范围

Question

我想根据多态关联的属性编写范围。

我有模型：

class Item < ApplicationRecord

  belongs_to :person, polymorphic: true

end

class Teacher < ApplicationRecord

  has_many :items, as: :person

end

class Student < ApplicationRecord

  has_many :items, as: :person

end

Teacher 和 Student 都具有 name 属性，我想将该属性用于以下范围：

scope :by_name, ->(name) { joins(:person).where(persons: {name: name}) }

既然我不能只提到范围，有什么办法可以很好地确定范围吗？

Answer 1

我不知道这样做的真正干净的方式......这很笨重但应该可以工作，但它不能很好地扩展。希望有人有更好的答案。

scope :by_name, ->(name) { joins("left join teachers on person_type = 'Teacher' and person_id = teachers.id")
                          .joins("left join students on person_type = 'Student' and person_id = students.id")
                          .where('teachers.name = ? OR students.name = ?', name, name) }

要处理名称数组，您可以按如下方式修改它...

scope :by_name, ->(*name) do
  name = name.flatten
  joins("left join teachers on person_type = 'Teacher' and person_id = teachers.id")
  .joins("left join students on person_type = 'Student' and person_id = students.id")
  .where('teachers.name IN (?) OR students.name IN (?)', name, name) 
end

这会让你做的

item.by_name('Smith')
item.by_name('Smith', 'Jones')
item.by_name(['Smith', 'Jones'])