What is the best way to convert an array to a hash in Ruby

Question

In Ruby, given an array in one of the following forms...

[apple, 1, banana, 2]
[[apple, 1], [banana, 2]]

...what is the best way to convert

Answer 1

The best way is to use Array#to_h:

[ [:apple,1],[:banana,2] ].to_h  #=> {apple: 1, banana: 2}

Note that to_h also accepts a block:

[:apple, :banana].to_h { |fruit| [fruit, "I like #{fruit}s"] } 
  # => {apple: "I like apples", banana: "I like bananas"}

Note: to_h accepts a block in Ruby 2.6.0+; for early rubies you can use my backports gem and require 'backports/2.6.0/enumerable/to_h'

to_h without a block was introduced in Ruby 2.1.0.

Before Ruby 2.1, one could use the less legible Hash[]:

array = [ [:apple,1],[:banana,2] ]
Hash[ array ]  #= > {:apple => 1, :banana => 2}

Finally, be wary of any solutions using flatten, this could create problems with values that are arrays themselves.