Question

我在Rails STI设置的父类中定义了一个回调和方法。

class Parent < ActiveRecord::Base
  before_save :populate_name

  # implicitly public
  def populate_name
    self.name = "foobar"
  end

class Child < Parent
end

当我像这样制作populate_name private或protected时：

class Parent < ActiveRecord::Base
  before_save :populate_name

  private
  def populate_name
    self.name = "foobar"
  end

class Child < Parent
end

然后我收到此错误：

NameError - undefined local variable or method `populate_name' for #<Child:0x007ff901eace30>:
  activemodel (3.2.16) lib/active_model/attribute_methods.rb:407:in `method_missing'
  activerecord (3.2.16) lib/active_record/attribute_methods.rb:149:in `method_missing'
  activesupport (3.2.16) lib/active_support/callbacks.rb:407:in `_run__3119425560225797910__save__1411052685854526397__callbacks'
  activesupport (3.2.16) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.16) lib/active_support/callbacks.rb:385:in `_run_save_callbacks'
  activesupport (3.2.16) lib/active_support/callbacks.rb:81:in `run_callbacks'
  activerecord (3.2.16) lib/active_record/callbacks.rb:264:in `create_or_update'
  activerecord (3.2.16) lib/active_record/persistence.rb:84:in `save'
  activerecord (3.2.16) lib/active_record/validations.rb:50:in `save'
  activerecord (3.2.16) lib/active_record/attribute_methods/dirty.rb:22:in `save'
  activerecord (3.2.16) lib/active_record/transactions.rb:259:in `block (2 levels) in save'
  activerecord (3.2.16) lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'
  activerecord (3.2.16) lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
  activerecord (3.2.16) lib/active_record/transactions.rb:208:in `transaction'
  activerecord (3.2.16) lib/active_record/transactions.rb:311:in `with_transaction_returning_status'
  activerecord (3.2.16) lib/active_record/transactions.rb:259:in `block in save'
  activerecord (3.2.16) lib/active_record/transactions.rb:270:in `rollback_active_record_state!'
  activerecord (3.2.16) lib/active_record/transactions.rb:258:in `save'
  app/controllers/child_controller.rb:135:in `create_or_update'

回调需要public吗？

Answer 1

儿童无法访问私人方法。受保护的方法可以。孩子无法使用私人方法。

When should we consider using private or protected?

Answer 2

保持这个问题以防万一有人用谷歌搜索这个问题（这是一个肥胖的手指）。

在模块结束之前，我意外地将私有部分放在课程结束之后。在最后一个结束之前，很容易抛出私有的，然后私有的方法，但是如果有嵌套的话，真的需要小心！

所以是的

将回调设为私人
如果您没有在Google查询中看到某些简单的内容，那么您必须有点胖的东西

module Foo
  class Parent < ActiveRecord::Base
    before_save :populate_name
  end

  private

  def populate_name
    self.name = "foobar"
  end
end

class Child < Parent
end

然后我收到此错误：

NameError - undefined local variable or method `populate_name' for #<Child:0x007ff901eace30>:
  activemodel (3.2.16) lib/active_model/attribute_methods.rb:407:in `method_missing'
  activerecord (3.2.16) lib/active_record/attribute_methods.rb:149:in `method_missing'
  activesupport (3.2.16) lib/active_support/callbacks.rb:407:in `_run__3119425560225797910__save__1411052685854526397__callbacks'
  activesupport (3.2.16) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.16) lib/active_support/callbacks.rb:385:in `_run_save_callbacks'
  activesupport (3.2.16) lib/active_support/callbacks.rb:81:in `run_callbacks'
  activerecord (3.2.16) lib/active_record/callbacks.rb:264:in `create_or_update'
  activerecord (3.2.16) lib/active_record/persistence.rb:84:in `save'
  activerecord (3.2.16) lib/active_record/validations.rb:50:in `save'
  activerecord (3.2.16) lib/active_record/attribute_methods/dirty.rb:22:in `save'
  activerecord (3.2.16) lib/active_record/transactions.rb:259:in `block (2 levels) in save'
  activerecord (3.2.16) lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'
  activerecord (3.2.16) lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'
  activerecord (3.2.16) lib/active_record/transactions.rb:208:in `transaction'
  activerecord (3.2.16) lib/active_record/transactions.rb:311:in `with_transaction_returning_status'
  activerecord (3.2.16) lib/active_record/transactions.rb:259:in `block in save'
  activerecord (3.2.16) lib/active_record/transactions.rb:270:in `rollback_active_record_state!'
  activerecord (3.2.16) lib/active_record/transactions.rb:258:in `save'
  app/controllers/child_controller.rb:135:in `create_or_update'

Rails STI，回调以及公共与私有

2 个答案: