Can I get the return value inside 'ensure' in Ruby?

Question

def some_method
  puts 'in method'
  return 'I am a return value'
ensure
  puts 'will print at the end'
  # Can I somehow get the return value of some_method here?
end

Is there some (possibly meta-programming) principle/way to get the return value of a method inside the "ensure" clause which is a part of the method definition (which we all know executes no matter what)?

Answer 1

Assign a Variable

Just make your return value a variable. You can use the variable inside your ensure statement, but the return value for the method will be the last statement evaluated in the non-exceptional part of the method. For example:

def some_method
  puts 'in method'
  value = 'I am a return value'
ensure
  puts 'will print at the end'
  puts value
  true
end

some_method
#=> "I am a return value"

Early Returns Work the Same

Note that the technique above works even if you return early, since the value passed to the return keyword is still the last non-exceptional expression evaluated. For example, the following method should never return false:

def return_true
  return value = true
  false
ensure
  puts value
  false
end

return_true
#=> true

Answer 2

Why do you need this in ensure? If the main part of the method completed w/o exception the return value of that part will be returned from the method (unless you do return in ensure). If exception happens, the return in your main part is not calculated at all.

Of course you can always use the following (very ugly IMO) code. But please don't do that. A better idea is to leave only the resource-cleanup code in the ensure block.

def some_method
  finished = false
  begin
    puts 'in method'
    result = 'I am a return value'
    finished = true
  ensure
    puts 'will print at the end'
    # Do whatever is needed for cleanup
    if finished
      # Here result is defined, you can manipulate it if needed
      return result
    end
  end
end