验证的至少一个在has_and_belongs_to_many [英] validate at least one in has_and_belongs_to_many

问题描述

我有一个模型：

has_and_belongs_to_many :users

我如何验证，该模型在模型中至少一个用户？我想：

How do I validate that the model has at least one user in the model? I tried:

validates_presence_of :users

但是，这似乎并没有给我什么，我想......

But that doesn't seem to give me what I want...

推荐答案

我会写自定义验证：

validate :has_users?

def has_users?
  errors.add_to_base "Model must have some users." if self.users.blank?
end

这将这样做。

That would do exactly that.

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