Reraise (same exception) after catching an exception in Ruby

Question

I am trying to improve my Ruby skills by catching exceptions. I want to know if it is common to reraise the same kind of exception when you have several method calls. So, would the following code make sense? Is it ok to reraise the same kind of exception, or should I not catch it on the process method?

class Logo   def process     begin       @processed_logo = LogoProcessor::create_image(self.src)     rescue CustomException       raise CustomException     end   end end  module LogoProcessor   def self.create_image     raise CustomException if some_condition   end end 

Answer 1

Sometimes we just want to know an error happened, without having to actually handle the error.

It is often the case that the one responsible for handling errors is user of the object: the caller. What if we are interested in the error, but don't want to assume that responsibility? We rescue the error, do whatever we need to do and then propagate the signal up the stack as if nothing had happened.

For example, what if we wanted to log the error message and then let the caller deal with it?

begin   this_will_fail! rescue Failure => error   log.error error.message   raise end 

Calling raise without any arguments will raise the last error. In our case, we are re-raising error.

In the example you presented in your question, re-raising the error is simply not necessary. You could simply let it propagate up the stack naturally. The only difference in your example is you're creating a new error object and raising it instead of re-raising the last one.

Answer 2

This will raise the same type of error as the original, but you can customize the message.

rescue StandardError => e   raise e.class, "Message: #{e.message}"