ruby-on-rails - 为什么我不能在 Ruby 中销毁这个变量？

Question

在 Rails 控制台中，我这样做:

input = Input.create :name => "foo"
=> #<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">
Input.all
=> [#<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">]
input
=> #<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">
input.destroy
=> #<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">
> Input.all
=> []
> input
=> #<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">
> input.reload
ActiveRecord::RecordNotFound: Couldn't find Input with id=8
> input
=> #<Input id: 8, name: "foo", created_at: "2013-05-07 11:45:17", updated_at: "2013-05-07 11:45:17">

我真正希望看到的是这样的:

> input
=> nil

对象已从数据库中删除，但变量仍然存在并且仍在尝试指向它。怎么回事？

Answer 1

input 变量存储对内存中实例的引用。销毁记录将从数据库中删除该行。尝试查找记录时调用 input.reload ( docs ) 会引发异常，但不会代表您将变量的值设置为 nil。

此行为在 DELETE 请求的范围内非常有用，您希望在该范围内显示有关已删除对象的信息。例如:

class WidgetsController < ApplicationController
  def destroy
    @widget = Widget.find(params[:id])
    @widget.destroy
    respond_with @widget, notice: "You successfully removed #{@widget.name}"
  end
end