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= Exception Handling
Exceptions are rescued in a +begin+/+end+ block:
begin
# code that might raise
rescue
# handle exception
end
If you are inside a method you do not need to use +begin+ or +end+ unless you
wish to limit the scope of rescued exceptions:
def my_method
# ...
rescue
# ...
end
The same is true for a +class+ or +module+.
You can assign the exception to a local variable by using <tt>=>
variable_name</tt> at the end of the +rescue+ line:
begin
# ...
rescue => exception
warn exception.message
raise # re-raise the current exception
end
By default StandardError and its subclasses are rescued. You can rescue a
specific set of exception classes (and their subclasses) by listing them after
+rescue+:
begin
# ...
rescue ArgumentError, NameError
# handle ArgumentError or NameError
end
You may rescue different types of exceptions in different ways:
begin
# ...
rescue ArgumentError
# handle ArgumentError
rescue NameError
# handle NameError
rescue
# handle any StandardError
end
The exception is matched to the rescue section starting at the top, and matches
only once. If an ArgumentError is raised in the begin section it will not be
handled in the StandardError section.
To always run some code whether an exception was raised or not, use +ensure+:
begin
# ...
rescue
# ...
ensure
# this always runs
end
You may also run some code when an exception is not raised:
begin
# ...
rescue
# ...
else
# this runs only when no exception was raised
ensure
# ...
end
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