ruby-on-rails - Rails ActiveRecord : pretty errors when deleting dependent entities with foreign keys constraints

Question

我在 Rails 应用程序中有几个带有外键约束的表。例如，每 订购 属于客户。有一个 客户_id 上的专栏订单 table 。

当我删除已下订单的客户时，由于数据库限制，MySQL 返回错误:

Mysql::Error: Cannot delete or update a parent row: a foreign key constraint fails (orders, CONSTRAINT orders_ibfk_2 FOREIGN KEY (customer_id) REFERENCES customers (id))

屏幕上弹出难看的错误，包括所有堆栈跟踪和那些东西
ActiveRecord::StatementInvalid 在 DevicesController#destroy ...

我想知道是否有一种优雅的方法来处理这些约束错误，比如“你可以删除这个对象，因为它与 X 相关联”

我怎么能做到？

Answer 1

在销毁之前的回调中使用react:

class Customer < ActiveRecord::Base
  before_destroy :no_referenced_orders
  has_many :orders

  private

  def no_referenced_orders
    return if orders.empty?

    errors.add_to_base("This customer is referenced by order(s): #{orders.map(&:number).to_sentence}")
    false # If you return anything else, the callback will not stop the destroy from happening
  end
end

在 Controller 中:

class CustomersController < ApplicationController
  def destroy
    @customer = Customer.find(params[:id])
    if @customer.destroy then
      redirect_to customers_url
    else
      render :action => :edit
    end
  end
end