How to split array of object by specific object field in ruby?

This code is ugly, how to do better?

todos = Todo.all

@todos_1 = Array.new
@todos_2 = Array.new
@todos_3 = Array.new

todos.each do |d开发者_高级运维oc|   
  if doc.category == nil 
    @ntodos_1 << doc 
  end
  if doc.category == "something" 
    @todos_2 << doc 
  end
  if doc.frame == "whatever" 
    @todos_3 << doc 
  end

You can use Todo.group("category").order("category") to organize the result set and then loop over it, knowing that when category changes you are at the next grouping.

Alternatively, it might be useful to create scopes for the Todo model:

class Todo < ActiveRecord::Base
  scope :something, where(:category => "something")
  scope :whatever, where(:category => "whatever")
end

This would allow you to assign the results to instance variables instead of iterating over all results within your controller:

@something = Todo.something
@whatever = Todo.whatever

Complementing the existing answer, let's assume you are working with "normal" Ruby objects, not a ORM:

todos_by_category = todos.group_by(&:category)

To be used:

>> todos_by_category["some_category"]
#=> [todo1, todo2, ...]

At least the first two if's could be combined in one case:

todos.each do |doc|   
  case doc.category 
    when nil 
      @ntodos_1 << doc 
    when "something" 
      @todos_2 << doc 
  end
  if doc.frame == "whatever" 
    @todos_3 << doc 
  end      

You also know elsif? }