Convert Array to Indexed Hash

array_to_hash.rb

# Often you'll have an array of hashes, and you find yourself needing to 
# retrieve an object from that array by some unique attribute of the hash.
#
# Here is a way to convert an array to a hash that contains hashes indexed by the key value you specify.

# This is possible because Array uses the Enumerable module as a mixin

users = [
  {'id' => 1, 'name' => 'Susan'},
  {'id' => 2, 'name' => 'Pat'},
  {'id' => 3, 'name' => 'Jason'}
]
search_user_hash = users.inject({}) { |map, user| map[user['id']] = user; map}

# search_user_hash = {
#   10932=>{"id"=>10932, "name"=>"Joe"},
#   10936=>{"id"=>10936, "name"=>"Susan"},
#   10943=>{"id"=>10943, "name"=>"Dan"}
# }
# joe = search_user[10932]
# susan = search_user_hash[10943]

Shouldn't the example:

# search_user_hash = {
#   1=>{"id"=>10932, "name"=>"Joe"},
#   2=>{"id"=>10936, "name"=>"Susan"},
#   3=>{"id"=>10943, "name"=>"Dan"}
# }

be this?

# search_user_hash = {
#   10932=>{"id"=>10932, "name"=>"Joe"},
#   10936=>{"id"=>10936, "name"=>"Susan"},
#   10943=>{"id"=>10943, "name"=>"Dan"}
# }

Yeah I'm definitely confused about what is going on here.

Does not seem to work everywhere as expected...:

 search_user_hash = users.inject({}) { |map, user| map[user['id']] = user; map}
=> {1=>{"id"=>1, "name"=>"Susan", 2=>{"id"=>2, "name"=>"Pat", 3=>{"id"=>3, "name"=>"Jason"}}},
 2=>{"id"=>2, "name"=>"Pat", 3=>{"id"=>3, "name"=>"Jason"}},
 3=>{"id"=>3, "name"=>"Jason"}}

perhaps you want this:

users = [{"id"=>1, "name"=>"Susan"}, {"id"=>2, "name"=>"Pat"}, {"id"=>3, "name"=>"Jason"}]
# => [{"id"=>1, "name"=>"Susan"}, {"id"=>2, "name"=>"Pat"}, {"id"=>3, "name"=>"Jason"}]
users.group_by{|x| x["id"]}
# => {1=>[{"id"=>1, "name"=>"Susan"}], 2=>[{"id"=>2, "name"=>"Pat"}], 3=>[{"id"=>3, "name"=>"Jason"}]}

@jemminger, yeah. You're right. My example output was off. I fixed it.

@LeFnord - Yeah. That's a nice approach too, but if you know that the 'id' is unique, then you can avoid working with arrays when accessing the resulting hash by ID.