Multiple return values with arrays and hashes - arrays

Question

I believe arrays are mostly used for returning multiple values from methods:
def some_method
return [1, 2]
end
[a, b] = some_method # should yield a = 1 and b = 2
I presume this is a kind of syntactic sugar that Ruby provides. Can we get a similar result with hashes, for instance
def some_method
return { "a" => 1, "b" => 2 }
end
{"c", "d"} = some_method() # "c" => 1, "d" => 2
I'm looking for the result { "c" => 1, "d" => 2 }, which obviously does not happen. Is there any other way this can be done? I know that we can return a hash from the method and store it and use it like so
def some_method
return {"a" => 1, "b" => 2}
end
hash = some_method()
Just curious if there is another way similar to the one with arrays but using hashes....
I think a simpler way to put the question would be...
# If we have a hash
hash = {"a" => 1, "b" => 2}
# Is the following possible
hash = {2, 3} # directly assigning values to the hash.
OR
# another example
{"c", "d"} = {2, 3} # c and d would be treated as keys and {2, 3} as respective values.

Answer 1

First of all, you have a syntax error. Instead of this:
[a, b] = [1, 2]
you should use:
a, b = [1, 2]
And if you want to use similar syntax with hashes, you can do:
a, b = { "c" => 1, "d" => 2 }.values # a => 1, b => 2
This is actually the same thing as the array version, beacause Hash#values returns an array of the hash values in the order they were inserted to the hash (because ruby hashes have a nice feature of preserving their order)

Answer 2

What you are asking is syntactically not possible.
What you want to accomplish is possible, but you will have to code it.
One possible way to do that is shown below
hash = {"a" => 1, "b" => 2}
# Assign new keys
new_keys = ["c", "d"]
p [new_keys, hash.values].transpose.to_h
#=> {"c"=>1, "d"=>2}
# Assign new values
new_values = [3, 4]
p [hash.keys, new_values].transpose.to_h
#=> {"a"=>3, "b"=>4}
If you really want some more easier looking way of doing, you could monkey-patch Hash class and define new methods to manipulate the values of keys and values array. Please be cautioned that it may not be really worthwhile to mess with core classes. Anyways, a possible implementation is shown below. Use at your own RISK.
class Hash
def values= new_values
new_values.each_with_index do |v, i|
self[keys[i]] = v if i < self.size
end
end
def keys= new_keys
orig_keys = keys.dup
new_keys.each_with_index do |k, i|
if i < orig_keys.size
v = delete(orig_keys[i])
self[k] = v
rehash
end
end
end
end
hash = {"a" => 1, "b" => 2}
hash.values = [2,3]
p hash
#=> {"a"=>2, "b"=>3}
hash.keys = ["c", "d"]
p hash
#=> {"c"=>2, "d"=>3}
hash.keys, hash.values = ["x","y"], [9, 10]
p hash
#=> {"x"=>9, "y"=>10}
hash.keys, hash.values = ["x","y"], [9, 10]
p hash
#=> {"x"=>9, "y"=>10}
# *** results can be unpredictable at times ***
hash.keys, hash.values = ["a"], [20, 10]
p hash
#=> {"y"=>20, "a"=>10}