More concise way of doing the grouping in Ruby

Ok so i have an array of 4 objects like

 => [#<Graphic id: 3...">, #<Collection id: 1....">, #<Category id:...">, #<Volume id: 15...">] 
 matches.size
 => 4 

with 4 different objects (Graphic, Collection, Category, Volume) I now need to separate these into 4 arrays based on the objects. So i created this method and it works but its so hackish....any ideas on how to achieve the same thing in a more concise way ...more rubyesk

Here is my method

def self.get_results(matches)
  graphics =  [], collections =  [], categories =  [], sub_categories =  []
  matches.group_by(&:class).each do |key, group|
    case group.first.class.to_s     
    when "Graphic"
     graphics << group
    when "Category"                
     categories << group
    when "SubCategory"      
     sub_categories << group
    when "Collection"        
     collections << group
    end
  end
  [graphics.flatten, collections.flatten, categories.flatten,开发者_StackOverflow社区 sub_categories.flatten]
end  

matches_by = matches.group_by {|m| m.class.to_s }
%w{Graphic Category SubCategory Collection}.map do |class_name|
  matches_by[class_name] || [] 
end

If you don't care what order they're in, try this

matches.group_by {|m| m.class.to_s }.values

If you just want a Hash, indexed by the class name (where the value of each entry is an Array of objects of that type), it's simply

matches.group_by {|m| m.class.to_s }

ret = {}
matches.group_by(&:class).each do |klass, item|
  ret[klass.to_s] = item
end
ret.values