Why can't I destroy this variable in Ruby? - ruby-on-rails

Question

In the rails console, I do this:
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">
What I'd really expect to see is something like:
> input
=> nil
The object is deleted from the database but the variable still exists and is still trying to point to it. What's going on?

Answer 1

The input variable stores a reference to the instance in memory. Destroying the record will remove the row from the database. Calling input.reload (docs) raises an exception when attempting to find the record but doesn't set the value of your variable to nil on your behalf.
This behavior can be useful in the span of a DELETE request in which you want to display information about the object you removed. For example:
class WidgetsController < ApplicationController
def destroy
#widget = Widget.find(params[:id])
#widget.destroy
respond_with #widget, notice: "You successfully removed #{#widget.name}"
end
end

Answer 2

The destroy method makes the SQL call to the database and destroys the row in the table that contains it. It does still allow you to manipulate the object in the application as long as it’s still in scope (i.e) the callbacks and
filters are allowed even after destroying the object.
It is better to use "delete" if we don't want the callbacks to be triggered or if we want better performance
you can use input.delete