Rails:保存后验证关联? [英] Rails: Validating association after save?

问题描述

我有一个 User 模型，它有很多 roles.角色包含一个 user_id 字段，我想validate_presence_of

I have a User model which has many roles. Roles contains a user_id field, which I want to validate_presence_of

问题是:如果我在创建时为用户分配角色，验证将失败，因为没有设置 user_id.现在，我确实想验证 user_id 是否存在，但我需要在检查之前保存用户.

The issue is: if I assign a role to user upon create, the validation fails because no user_id is set. Now, I do want to validate that a user_id exists, but I need to save the user before checking that.

当前代码如下所示:

@user = User.new(params[:user])
@user.roles << Role.new(:name => 'Peon') unless @user.has_roles?
if @user.save
  # ...

我能想到的解决问题的唯一方法是禁用验证(我不想这样做)或双重保存到数据库中，这并不完全有效.

The only ways I can think of getting around the problem involves either disabling the validation, which I don't want to do, or double-saving to the DB, which isn't exactly efficient.

处理这个问题的标准方法是什么?

What's the standard way for handling this issue?

推荐答案

我认为如果您将代码更改为如下所示，您可以解决验证问题:

I think you can get around the validation problem if you change your code to look like this:

@user = User.new(params[:user])
@user.roles.new(:name => 'Peon') unless @user.has_roles?
if @user.save
  # ...

如果这不起作用，您可以尝试将验证更改为:

If that doesn't work, you could try changing you validation to this:

class Role < ActiveRecord::Base
  belongs_to :user
  validates :user_id, :presence => true, :unless => Proc.new() {|r| r.user}
end

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