Rails - 检查父模型属性是否存在

Question

我想显示已将其帐户连接到我们的付款购买提供商的教师列表。当教师连接他们的付款帐户时，它会更新 User 模型上的付款 uid 字段。

我们的模型是这样设置的：

class User < ActiveRecord::Base
    has_one :teacher

class Teacher
    belongs_to :user

我的老师控制器：

class TeachersController < ApplicationController
    def index
        @teachers = Teacher.order('created_at DESC')
    end

我想显示如下内容：

@teachers = Teacher.where(self.user.uid.present?).order('created_at DESC')

但是我返回了一个 NoMethodError 'undefined method `user' for TeachersController'

Answer 1

试试：

@teachers = Teacher.joins(:user).where.not('users.uid = ?',nil).order(created_at: :desc)

或

valid_users = User.where.not(uid: nil).pluck(:id) # return array of all user's id which has not uid nil
@teachers = Teacher.where(user_id: valid_users).order(created_at: :desc) 

Answer 2

假设您想要拥有用户的教师？

@teachers = Teacher.where.not(user_id: nil).order(created_at: :desc)

Answer 3

使用范围方法：

class Teacher < ActiveRecord::Base
  ...
  def self.connected
    includes(:user).where.not(users: { uid: nil }).references(:user)
  end
  ...

end

你会像这样使用它：

@teacher = Teacher.connected.order('created_at DESC')