How to return multiple values in ruby

You can return multiple values on a method using comma-separated values when you return the data.

Check the example below

def multiple_values
  return 1, 2, 3, 4
end

Here we are creating a method called multiple_values that return 4 values. Each of them separated by a comma, in this form when we call multiple_values as a result, we will see an array with all these values. So the first one 1 will be at position 0 of the array, 2 will be at position 1, 3 will be at position 2 and the last value 4 will be at position 3 of the array.

Let’s call our multiple_values method

def print_values
  values = multiple_values

  _1 = values.first
  _2 = values[1]
  _3 = values[2]
  _4 = values[3]

  p "first - #{_1}, two - #{_2}, three - #{_3}, four - #{_4}" 
  # => "first - 1, two - 2, three - 3, four - 4"
end

print_values

Calling the method

We created a method called print_values that will print the values of the array returned by multiple_values method.
As you can see we store the array returned by multiple_values in a variable called values, this values now contain all the values that we returned before. So for this example to show clearly what values contain we created a variable for each value of the array. Variable _1 called a shortcut method of the array to retrieve the first element of the array even though it will work exactly the same way as values[0]. Then we have the rest of the variables _2, _3, _4 to store the remaining values.

In the last line of the method, we print with a custom format the variables. So to make this work don’t forget to call print_values to see what it does.

If you are the kind of person that likes to play with the code. Here is the link of the live version https://repl.it/@ViriCruz/multiplevalues

Feel free to play around with the code.

Comments

[Oinak]

That is a very neat explanation, thanks for sharing!

I see your post is centered on the how and not on the why.

One of the most common errors in ruby is:

NoMethodError: undefined method 'foo' for nil:NilClass

It comes from calling a method on the result of a function that we forgot could return nil.

Usually, when I feel tempted to return mutiple or complex values, I tend to:

A) Return a hash than documents what they are:

  def complex_value
    thing = some_query
    {
      status: (thing ? :ok : :not_found),
      content: thing.something
    } # always responds to [:status] and [:content]
  end

B) Return an object with a NullObject pattern to avoid nil.something down the line.

class Result
  attr_reader :name, :other
  def initialize(value)
    @name = value ? value.name : 'Not found'
    @price = value ? " $#{value.amount} " : '-'
  end
end

def complex_value
  thing = some_query
  Result.new(thing) # always responds to '.name' and '.price'
end

I know the example is a bit contrived due to brevity, but I hope it lets my point though.

What do you think?

P.S.: Sandi Metz on this matters

[ViriCruz]

Yes, you're right NoMethodError: undefined method 'foo' for nil:NilClass this a very common error in ruby and I understand your point of view. Thanks for sharing your opinions! 😁

[Michael Currin]

Thanks, I was looking for how to return a tuple.

Tip - you can unpack all the variables in one line.

def foo
  return "abc", 2, true
end

a, b, c = foo()
a
# "abc"
b
# 2
c
# true