验证嵌套属性presence [英] Validate presence of nested attributes

问题描述

我如何验证模型具有使用嵌套的属性至少有一个关联的模型？这是推动我疯了，因为我相信，我失去了一些东西简单。例如，我想要求一个列表总是至少有一个任务。

How do I validate that a model has at least one associated model using nested attributes? This has been driving me crazy as I am sure that I am missing something simple. For example, I want to require that a List always has at least one Task.

class List < ActiveRecord::Base
  has_many :tasks, :dependent => :destroy
  accepts_nested_attributes_for :tasks, :allow_destroy => true
end

class Task < ActiveRecord::Base
  belongs_to :list
end

我已经尝试了许多不同的选择。

I've tried many different options.

1 - 增加一个验证，以列表：

1- adding a validation to lists:

def validate
  if self.tasks.length < 1
    self.errors[:base] << "A list must have at least one task."
  end
end

但这将仍然允许你删除删除任务清单的验证发生之前的任务被破坏时，由于一个现有列表中的所有任务。

but this will still allow you to delete all the tasks of an existing list since when deleting tasks the validation of list happens before the tasks are destroyed.

2 - 检查，看是否有任务不标记为破坏的before_save回调

2- checking to see if any tasks are not marked for destruction in a before_save callback

before_save :check_tasks

private
#look for any task which won't be deleted
def check_tasks
  for t in self.tasks
    return true if ! t.marked_for_destruction?
  end
  false  
end

由于某种原因，我不能让它永远删除任务与任何遍历一个列表的任务。同样如此，如果我做此项检查在高清验证，而不是回调

3，要求任务的presence validates_ presence_of：任务，但是这一点，永远不会删除任何任务

3- requiring the presence of tasks validates_presence_of :tasks, but with this it won't ever delete any tasks

推荐答案

我结束了扩大杂志的保存方法来解决这个问题。它的工作就像一个魅力。

I ended up extending Magazine's save method to get around the problem. It worked like a charm.

def save
  saved = false
  ActiveRecord::Base.transaction do
    saved = super
    if self.conditions.size < 1
      saved = false
      errors[:base] << "A rule must have at least one condition."
      raise ActiveRecord::Rollback
    end
  end
  saved
end

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