aborting a composed method early on failure

aborting_composed_method.rb

# is this the best way to do it?
# in this way, each method must raise if something goes wrong, 
# but this behavior isn't necessarily exceptional. composed_method 
# uses this exception for control flow because its contract is that 
# it returns true on success, false on failure. 
# I've cargo culted the phrase "don't use exceptions for control flow" but I realize I don't know why...
def composed_method
  frobulate_widgets
  refrobulate_widgets
  confribulate_frobulations
  true
rescue FrobulationError
  false
end

It's hard to discuss it on such a high level example, but how about:

def composed_method
  frobulate_widgets && refrobulate_widgets && confribulate_frobulations
end

Assuming that each of them returns boolean value, in case one of them fails it won't proceed to the next and return false as expected. Otherwise it will return true.

If the assumption doesn't hold (some of them don't return boolean value) you can wrap them.

But at the end of the day, "it depends". In some cases the pattern you showed (to rescue an exception) will be acceptable too.