Some quick explanations about when return is unnecessary in Ruby, as well as the guard pattern.

gistfile1.md

Ruby has implicit returns. This means that if a return is the last expression in a path of execution, there's no need for the return keyword.

Worth noting is that return's default argument is nil, which is a falsey value.

def foo
  do_stuff
  return
end

def bar
  return do_more_stuff
end

is equivalent to:

def foo
  do_stuff
  nil
end

def bar
  do_more_stuff
end

Depending on what foo is doing, returning nil may or may not actually be necessary.

---

def foo
  return raise SomeException

  do_something
end

This is equivalent to:

def foo
  return(raise(SomeException))

  do_something
end

which means it calls raise() first. raise() immediately changes the path of execution, and thus the return is never ran -- it's effectively dead code.

---

If there is an unconditional raise() followed immediately by an unconditional return(), it's unnecessary for the same reasons as above.

def bar
  if some_condition
    raise SomeException
    return
  end
end

---

In this case, both the raise() and return() calls are conditional, so they are both required.

def baz
  if condition_one
    raise SomeException if condition_two
    return unless condition_three

    # <actual useful code here>
  end
end

---

Time for a slight diversion for something that caught my eye in the last section.

return unless X/return if X/raise unless X/raise if X is sometimes referred to as the "guard pattern."

It serves two purposes, and in many cases can make code considerably easier to reason about (for me, anyway):

1. Clustering lists of terminating conditions
2. Reducing levels of indentation

def asdf
  if condition_one
    # code
  else
    raise SomeException
  end
end

def fdsa
  if condition_one
    # Code blob #1
  else
    return
  end

  # Code blob #2
end

The above two functions can become this:

def asdf
  raise SomeException unless condition_one

  # code
end

def fdsa
  return unless condition_one

  # Code blob #1
  # Code blob #2
end