Alternatives to convert a array to a hash using same keys and values

Question

I want to convert:

[:one, :two, :three]

to:

{one: :one, two: :two, three: :three}

So far I'm using this:

Hash[[:basic, :silver, :gold, :platinum].map { |e| [e, e] }]

But I would like to know if it's possible by some other way?

This is to use in a Rails enum definition in model, to save values as strings in db.

Answer 1

Array#zip:

a = [:one, :two, :three]
a.zip(a).to_h
#=> {:one=>:one, :two=>:two, :three=>:three}

Array#transpose:

[a, a].transpose.to_h
#=> {:one=>:one, :two=>:two, :three=>:three}

Answer 2

I prefer constructing hashes from scratch rather than constructing a temporary array (which consumes memory) and converting it to a hash.

[:one, :two, :three].each_with_object({}) { |e,h| h[e]=e }
  #=> {:one=>:one, :two=>:two, :three=>:three}

Answer 3

In Ruby on Rails 6+ it is possible to use Enumerable#index_with

If combine it with Object#itself, it will look such way:

%i[one two three].index_with(&:itself)

# => {:one=>:one, :two=>:two, :three=>:three}

And yes, it is convenient to use enum to declare strings stored in the database with hash such way

enum my_attribute: MY_ARRAY.index_with(&:itself)

Answer 4

Here is another way with map:

>> [:one, :two, :three].map { |x| [x,x] }.to_h
=> {:one=>:one, :two=>:two, :three=>:three}