Handle default exception in ruby - ruby

Question

How do I implement default behavior for an Exception? begin rescue else doesn't work(which I think should).
And, isn't else meaningless in the scenario? Any code that has to run when no exception is raised does run between the begin-rescue block.
By the way I have the following workaround, but I'm not satisfied with it.
class MyException < Exception
end
class YourException < Exception
end
begin
raise MyException if 2 > 50
raise YourException if 1 < 90
rescue Exception => e
case e.message
when /MyException/
puts "MyException Caught"
else
puts "Default Exception Caught"
end
end

Answer 1

First of all, you really shouldn't subclass Exception. It is the superclass of all Ruby exceptions, including NoMemoryError, SyntaxError, Interrupt, SystemExit; all of which you don't normally need to rescue from. Doing so, whether accidentally or on purpose, is discouraged since it can prevent a program from exiting properly, even if it was interrupted by the user. It can also hide or produce some quite obscure bugs.
What you want to subclass is StandardError, which is the superclass of most Ruby errors we see in day-to-day programming. This class is also the one which will be rescued should you not specify one:
begin
object.do_something!
rescue => error # will rescue StandardError and all subclasses
$stderr.puts error.message
end
I believe this is the "default behavior" you are looking for. You can handle a specific error, then all other errors in general:
class CustomApplicationError < StandardError
end
begin
object.do_something!
rescue CustomApplicationError => error
recover_from error
rescue => error
log.error error.message
raise
end
The else clause is not meaningless in error handling. It will execute the nested code if and only if no exceptions were raised, as opposed to the ensure clause which will execute code regardless. It allows you to handle success cases.
begin
object.do_something!
rescue => error
log.error error.message
else
log.info 'Everything went smoothly'
end

Answer 2

First, I do not understand why you are case-conditioning with the error message. Why not do it with the error itself by their class? Then, it would be like this:
begin
raise MyException if 2 > 50
raise YourException if 1 < 90
rescue Exception => e
case e
when MyException
puts "MyException Caught"
else
puts "Default Exception Caught"
end
end
Second, doing it as above is not the straightforward way. The correct way to do it is:
begin
raise MyException if 2 > 50
raise YourException if 1 < 90
rescue MyException
puts "MyException Caught"
rescue Exception
puts "Default Exception Caught"
end
If YourException were a subclass of StandardError, then it could be captured by rescue without specifying the exception class.