return the two and more values from the method

Question

Is there any possibility to return multiple values from method? Something like this:

def do()
  return ["a", 10, SomeObject.new]
end

[a, b, c] = do

Answer 1

>> def sumdiff(x,y)  
>> return x+y,x-y  
>> end  
=> nil  

>> sumdiff(3,4)  
=> [7, -1]  

>> a = sumdiff(3,4)  
=> [7, -1]  
>> a  
=> [7, -1]  

>> a,b=sumdiff(3,4)  
=> [7, -1]  
>> a  
=> 7  
>> b  
=> -1  

>> a,b,c=sumdiff(3,4)  
=> [7, -1]  
>> a  
=> 7  
>> b  
=> -1  
>> c  
=> nil

Answer 2

Whilst returning multiple values is often useful, I usually find it's a pointer to a new object requirement.

That is, I usually find that those return values are closely tied together in meaning/context and are passed around as such. So in these cases I would create a new object to tie these together. It's a particular code smell I've learnt to recognise.

Answer 3

Ruby has a limited form of destructuring bind:

ary = [1, 2, 3, 4]
a, b, c = ary
p a # => 1
p b # => 2
p c # => 3

a, b, *c = ary
p c # => [3, 4]

a, b, c, d, e = ary
p d # => 4
p e # => nil

It also has a limited form of structuring bind:

 a = 1, 2, 3
 p a # => [1, 2, 3]

You can combine those two forms like so:

a, b = b, a # Nice way to swap two variables

a, b = 1, 2, 3
p b # => 2

def foo; return 1, 2 end
a, b = foo
p a # => 1
p b # => 2

There's several other things you can do with destructuring / structuring bind. I didn't show using the splat operator (*) on the right hand side. I didn't show nesting (using parantheses). I didn't show that you can use destructuring bind in the parameter list of a block or method.

Here's just an appetizer:

def foo(((a, b, c, d), e, *f), g, *h)
  local_variables.sort.each do |lvar| puts "#{lvar} => #{eval(lvar).inspect}" end
end

foo([[1, 2, 3], 4, 5, 6], 7, 8, 9)
# a => 1
# b => 2
# c => 3
# d => nil
# e => 4
# f => [5, 6]
# g => 7
# h => [8, 9]