进行救援的最佳方法

Question

Is this the correct way to do a rescue in a block?

Also, is it the shortest?

def rescue_definition
    begin
        user.begin_rescue
    rescue Example::ParameterValidationError => e
        redirect_to :back, error: e.message_to_purchaser
    rescue Example::ProcessingError => e
        redirect_to :back, error: e.message_to_purchaser
    rescue Example::Error
        redirect_to :back, error: e.message_to_purchaser
    else
        if user
            flash['success'] = 'OK'
        else
            flash['error'] = 'NO'
        end
    end
    redirect_to :back
end

Answer 1

The idea to use begin, rescue, ensure is to put the methods than can generate an error in the begin block, then you can handle the errors in one o more rescue blocks and finally you can put an optional ensure block for sentences that you want to execute on both success or fail scenarios for example release resources.

When you want all the method be handled by begin, rescue, ensure blocks, then begin keyword is optional, you can use or not the keyword, since you are asking for the shortest option, you will need to do some minor changes to your code:

def rescue_definition
  user.begin_rescue
  # and any other stuff you want to execute
  if user
    flash['success'] = 'OK'
  else
    flash['error'] = 'NO'
  end
  redirect_to :back
rescue Example::ParameterValidationError => e
  redirect_to :back, error: e.message_to_purchaser
rescue Example::ProcessingError => e
  redirect_to :back, error: e.message_to_purchaser
rescue Example::Error
  redirect_to :back, error: e.message_to_purchaser
end

If you want it even shorter you can rescue multiple exception types in one rescue block:

def rescue_definition
  user.begin_rescue
  # and any other stuff you want to execute
  if user
    flash['success'] = 'OK'
  else
    flash['error'] = 'NO'
  end
  redirect_to :back
rescue Example::ParameterValidationError, Example::ProcessingError, Example::Error => e
  redirect_to :back, error: e.message_to_purchaser
end

Answer 2

Aguar's post handles the current implementation. If you handle all the errors the same way then you can have them inherit from a custom class and just catch them all with 1 rescue call.

def stuff
  user.stuff
  if user
    flash['success'] = 'Ya'
  else
    flash['error'] = 'Nah'
  end
  redirect_to ....
rescue CustomClassError => e
  redirect_to :back, error: e.message_to_purchaser
rescue NonCustomErrors => e
  #handle it
end