RABL - Render collection as object with the ids as keys - ruby-on-rails

Question

In Ruby on Rails 4, I'm trying to make an API for my website and instead of using an array like so:
[{id: 1, name: "John"}, {id: 2, name: "Foo"}, {id: 3, name: "Bar"}]
I want to render it like this, because it makes it much easier to search through in javascript (and for other reasons):
{"1": {id: 1, name: "John"}, "2": {id: 2, name: "Foo"}, "3": {id: 3, name: "Bar"}}
This works:
# users/index.rabl
#users.each do |user|
node(users.id.to_s) do
partial('api/v1/users/show', object: user)
end
end
But in the partial, I want another collection of elements (which belong to the user) and I can't get that working. Is there a more elegant way to do this?

Answer 1

To choose hash-map rather than array is definitely better option if have control on API backend codebase. From BigO notation hash lookup happens with constant O(1) time, not O(n) as for array.
Primary key lookup from the database is the most performant way to query data. Primary key is usually short and always indexed. In case of big data set use pagination.
Let's assume there is no RABL (you can always instantiate pure Ruby classes in RABL DSL code) but just an array:
array = [{id: 1, name: "John"}, {id: 2, name: "Foo"}, {id: 3, name: "Bar"}]
hash = {}
array.each{ |elem,i| hash[elem[:id].to_s] = elem }
# {"1"=>{:id=>1, :name=>"John"}, "2"=>{:id=>2, :name=>"Foo"}, "3"=>{:id=>3, :name=>"Bar"}}
To pass the Ruby hash to Javascript on client you probably want to encode it appropriately:
# hash.to_json
# {"1":{"id":1,"name":"John"},"2":{"id":2,"name":"Foo"},"3":{"id":3,"name":"Bar"}}
From Javascript you query hash by its key:
hash = {"1":{"id":1,"name":"John"},"2":{"id":2,"name":"Foo"},"3":{"id":3,"name":"Bar"}}
hash[1]
# Object { id=1, name="John"}