Rubyonrails 您如何查看在 Rails 中触发回调的关联模型

如果将相应的关联添加到Contact，则可以在after_commit回调中访问它们:

class Student < ApplicationRecord
  belongs_to :contact
  accepts_nested_attributes_for :contact
end

class Teacher < ApplicationRecord
  belongs_to :contact
  accepts_nested_attributes_for :contact
end

class Contact < ApplicationRecord
  has_one :teacher
  has_one :student

  after_commit do
    p teacher || student
  end
end

>> Teacher.create(contact_attributes: { name: 'teacher' })
...
# after_commit START
#<Teacher id: 1, contact_id: 1>
# after_commit END
=> #<Teacher:0x00007fd28056a9f0 id: 1, contact_id: 1>

需要注意的一点是，如果老师不在场，它会影响数据库:

>> Student.create(contact_attributes: { name: 'student' });
 ...
# after_commit START
  Teacher Load (0.4ms)  SELECT "teachers".* FROM "teachers" WHERE "teachers"."contact_id" = $1 LIMIT $2  [["contact_id", 2], ["LIMIT", 1]]
#<Student id: 1, contact_id: 2>
# after_commit END
=> #<Student:0x00007fd2837bd9c0 id: 1, contact_id: 2>

切换到多态关系也是一种解决方案:

class Student < ApplicationRecord
  has_one :contact, as: :contactable
  accepts_nested_attributes_for :contact
end

class Teacher < ApplicationRecord
  has_one :contact, as: :contactable
  accepts_nested_attributes_for :contact
end

# NOTE: to add plymorphic relationship add this to contact migration:
#       t.references :contactable, polymorphic: true
class Contact < ApplicationRecord
  belongs_to :contactable, polymorphic: true

  after_commit do
    p contactable
  end
end

>> Student.create(contact_attributes: { name: 'student' })
 ...
# after_commit START        
#<Student id: 1>            
# after_commit END          
=> #<Student:0x00007f4a85c0d1c8 id: 1>

>> Teacher.create(contact_attributes: { name: 'teacher' })
 ...
# after_commit START        
#<Teacher id: 1>            
# after_commit END          
=> #<Teacher:0x00007f4a884e2a08 id: 1>

Update

如果将回调设置为Student和Teacher，则无论上述设置如何，都可以访问所有内容.

多态性:

class Teacher < ApplicationRecord
  has_one :contact, as: :contactable
  accepts_nested_attributes_for :contact

  after_commit do
    p self
    p contact
    p contact.previous_changes
  end
end

>> Teacher.create(contact_attributes: { name: 'teacher' })
 ...
# after_commit START
#<Teacher id: 1>
#<Contact id: 1, name: "teacher", contactable_type: "Teacher", contactable_id: 1>
{"id"=>[nil, 1], "name"=>[nil, "teacher"], "contactable_type"=>[nil, "Teacher"], "contactable_id"=>[nil, 1]}
# after_commit END
=> #<Teacher:0x00007fbf1bdd2db8 id: 1>

属于\u:

class Teacher < ApplicationRecord
  belongs_to :contact
  accepts_nested_attributes_for :contact

  after_commit do
    p self
    p contact
    p contact.previous_changes
  end
end

>> Teacher.create(contact_attributes: { name: 'teacher' })
   ...
# after_commit START        
#<Teacher id: 1, contact_id: 1>
#<Contact id: 1, name: "teacher">
{"id"=>[nil, 1], "name"=>[nil, "teacher"]}
# after_commit END          
=> #<Teacher:0x00007f9f2ce6a730 id: 1, contact_id: 1>

如果Contact中必须有after_commit，则必须明确告诉Contact更新来自Teacher或Student:

class Teacher < ApplicationRecord
  belongs_to :contact
  accepts_nested_attributes_for :contact

  # NOTE: before saving, let contact know it's about to be updated
  #       by Teacher.
  before_save do
    contact.updated_from = :teacher
  end
end

class Contact < ApplicationRecord
  # NOTE: just a temporary attribute
  attr_accessor :updated_from

  after_commit do
    print 'Updated from: '
    p self.updated_from
  end
end

>> Teacher.create(contact_attributes: { name: 'teacher' })
 ...
# after_commit START
Updated from: :teacher      
# after_commit END
=> #<Teacher:0x00007fd6a40459c0 id: 1, contact_id: 1>

或在教师中没有before_save个回调:

>> Teacher.create(contact_attributes: { name: 'teacher', updated_from: 'teacher' })
 ...
Updated from: "teacher"  

或重写contact_attributes=方法:

class Teacher < ApplicationRecord
  belongs_to :contact
  accepts_nested_attributes_for :contact

  def contact_attributes= attributes
    attributes[:updated_from] = :teacher
    super
  end
end