return-the-thing-being-printed.md

Return The Thing Being Printed

The puts method is the canonical way of priting things to stdout in Ruby. Notably, its return value is always nil. Generally this isn't much of an issue, but can be a potential gotcha while debugging.

Consider the following method whose behavior you are trying to investigate:

def process(arg)
  thing = do_something(arg)

  thing.value
end

I want to print out the value of thing when I execute the code to see what it is while debugging. So I add a puts statement.

def process(arg)
  thing = do_something(arg)

  puts thing.value
end

Well, I just broke the behavior of process because it now returns nil instead of thing.value.

I could add an additional line that returns the correct value. Or I could use p which both prints its argument to stdout and returns it as is.

def process(arg)
  thing = do_something(arg)

  p thing.value
end

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