Implement the repository pattern with a strategy object (to swap out with an AR model)

repository_pattern.rb

class InMemoryStore
  attr_accessor :result_set
  def initialize
    @result_set = []
  end

  def store(row)
    !!(result_set << row)
  end

  def all
    result_set
  end

  def where(criteria={})
    return result_set unless criteria
    selected_rows = result_set
    criteria.each_pair do |attribute,value|
      selected_rows = if value
        selected_rows.select {|row| row[attribute] == value }
      else
        selected_rows.reject {|row| row[attribute] }
      end
    end
    selected_rows
  end

  def count
    result_set.count
  end
end

class Repository
  attr_reader :strategy
  def initialize(strategy)
    @strategy = strategy
  end

  def store(args)
    !!strategy.store(args)
  end

  def where(args)
    strategy.where(args)
  end

  def all
    strategy.all
  end

  def count
    strategy.count
  end
end

Item = Class.new(Struct.new(:ref, :name))

a = Item.new(1, 'A')
b = Item.new(2, 'B')
c = Item.new(3, 'C')

repo = Repository.new(InMemoryStore.new)

repo.store(a)
repo.store(b)

repo.where(name: 'A') # => [#<struct Item ref=1, name="A">]
repo.where(ref: 2)[0].name # => "B"

repo.count # => 2
repo.all # => [#<struct Item ref=1, name="A">, #<struct Item ref=2, name="B">]

repo.store(c)
repo.where(ref: 3) # => [#<struct Item ref=3, name="C">]