Ruby : Generate a Hash of Hashes from an Array of Hashes

Question

I have the following

friends = [{ name: "Jack", attr1:"def", attr2:"def" }, { name: "Jill", attr1:"def", attr2:"def" }]

I want to convert the above representation into a hash of hashes like this

friends = { "Jack" => { attr1: "def", attr2:"def" }, "Jill" => { attr1: "def", attr2: "def" } }

Any elegant way of doing this in Ruby ?

Answer 1

Hash[friends.map { |f| _f = f.dup; [_f.delete(:name), _f] }]
# => {"Jack"=>{:attr1=>"def", :attr2=>"def"}, "Jill"=>{:attr1=>"def", :attr2=>"def"}}

Answer 2

friends.each_with_object({}) do |f, o|
    f = f.dup
    o[f.delete :name] = f
end

Answer 3

hash = {}
friends.each{|h| hash[h.delete(:name)] = h }
# => {"Jack"=>{:attr1=>"def", :attr2=>"def"}, "Jill"=>{:attr1=>"def", :attr2=>"def"}}

Answer 4

When you want to transform one array into another, use collect :

friends = Hash[
  friends.collect do |f|
    _f = f.dup
    name = _f.delete(:name)
    [ name, _f ]
  end
]

You can create a new hash easily using Hash[] and provide it an array with a series of key/value pairs in it. In this case the name field is removed from each.

Answer 5

If we understand "elegant" as the way to write concise code by leveraging reusable abstractions, I'd write:

require 'active_support/core_ext/hash'
require 'facets/hash'
friends.mash { |f| [f[:name], f.except(:name)] }

No need to add gem dependencies for these two fairly big libraries, you can always implement the individual methods in your extensions library.