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copied!<p>It depends (as always). You could use an array subclass and you you could build a custom class and use composition and delegation. Here's a simple example with an array subclass:</p> <pre><code>class DinosaurArray < Array def carnivores select { |dinosaur| dinosaur.type == :carnivore } end def herbivores select { |dinosaur| dinosaur.type == :herbivore } end def each_carnivore(&block) carnivores.each(&block) end def each_herbivore(&block) herbivores.each(&block) end end </code></pre> <p>And here's a simple one with composition and delegation:</p> <pre><code>class DinosaurArray def initialize @array = [] end def <<(dinosaur) @array << dinosaur end def carnivores @array.select { |dinosaur| dinosaur.type == :carnivore } end def herbivores @array.select { |dinosaur| dinosaur.type == :herbivore } end def each(&block) @array.each(&block) end def each_carnivore(&block) carnivores.each(&block) end def each_herbivore(&block) herbivores.each(&block) end end </code></pre> <p>Both implementation can be used like this:</p> <pre><code>require 'ostruct' dinosaurs = DinosaurArray.new dinosaurs << OpenStruct.new(type: :carnivore, name: "Tyrannosaurus") dinosaurs << OpenStruct.new(type: :carnivore, name: "Allosaurus") dinosaurs << OpenStruct.new(type: :herbivore, name: "Apatosaurus") puts "Dinosaurs:" dinosaurs.each.with_index(1) { |dinosaur, i| puts "#{i}. #{dinosaur.name}" } puts </code></pre> <p>But also has custom iterators:</p> <pre><code>puts "Carnivores:" dinosaurs.each_carnivore.with_index(1) { |dinosaur, i| puts "#{i}. #{dinosaur.name}" } puts puts "Herbivores:" dinosaurs.each_herbivore.with_index(1) { |dinosaur, i| puts "#{i}. #{dinosaur.name}" } </code></pre> <p>Output:</p> <pre><code>Dinosaurs: 1. Tyrannosaurus 2. Allosaurus 3. Apatosaurus Carnivores: 1. Tyrannosaurus 2. Allosaurus Herbivores: 1. Apatosaurus </code></pre>

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