在销毁之前验证

Question

我有三个类:School,Account,和Administratorship.

学校

has_many :administatorships
has_many :administrators, :through => :administratorships

帐户

has_many :administratorships

管理人的职位

belongs_to :account
belongs_to :school

before_destroy :confirm_presence_of_alternate_administratorship_in_school

protected

def confirm_presence_of_alternate_administratorship_in_school
    unless school.administrators.count(["administratorships.account_id != #{id}"]) > 0
        errors.add_to_base "The school must have at least one administrator"
    end
end

现在,我想要发生的是当我调用destroy一个实例时Administratorship,它会向模型添加错误并防止模型的破坏.我已删除该unless语句以查看是否阻止添加错误,但事实并非如此.似乎模型上有错误并不能防止破坏发生.

所以我的问题是,有什么方法可以防止使用验证发生破坏？我意识到我可以定义一个仅在满足上述条件时才会销毁的方法,但似乎验证方法是一种更优雅的解决方案.

Answer 1

如果从before_destroy方法返回false,则会阻止销毁.

Answer 2

这是一个Rails 5的答案,如果你返回false,它会给出一个弃用警告:"返回falseActive Record和Active Model回调不会隐式停止Rails 5.1中的回调链".

def confirm_presence_of_alternate_administratorship_in_school
  return if school.administrators.count(["administratorships.account_id != #{id}"]) > 0
  errors[:base] << 'The school must have at least one administrator'
  throw :abort
end

Answer 3

false从验证方法返回将阻止记录被销毁.

例:

def confirm_presence_of_alternate_administratorship_in_school
  unless school.administrators.count(["administratorships.account_id != #{id}"]) > 0
    # errors.add_to_base() is deprecated in Rails 3. Instead do...
    errors.add(:base, "The school must have at least one administrator")

    # this will prevent the object from getting destroyed
    return false
  end
end

附注:我无法显示此错误消息.验证将起作用,对象不会被删除,但没有消息让我知道发生了什么.原因是控制器重定向到索引视图而不是渲染删除视图(例如,如果在创建新用户时出现错误,它将呈现:action =>'new'.在这种情况下,有没有删除视图).发生这种情况时,实际上正在重置设置了错误消息的实例变量(在errors.add(:base,"message")中),这会破坏进程中的错误.