gistfile1.rb

class Container
  def initialize injections
    @injections = injections
    @resolved = {}
  end

  def have? token
    !get_injection(token).nil?
  end

  def get token
    lookup(token)
  end

  private

  def get_injection token
    token_tree = token.split(".").map(&:to_sym)
    token_tree.reduce(@injections) do |current_level, token|
      current_level && current_level[token]
    end
  end

  def lookup token
    token = token.to_s
    return @resolved[token] if @resolved[token]      
    injection = get_injection(token)

    if injection.is_a? Proc
      @resolved[token] = injection.call
    elsif injection.is_a? Class
      @resolved[token] = injection.new
    elsif injection.is_a? Array
      klass_or_proc = injection.first
      resolved_dependencies = injection.drop(1).map { |d| lookup(d) }
  
      if klass_or_proc.respond_to?(:call)
        @resolved[token] = klass_or_proc.call(*resolved_dependencies)
      else 
        @resolved[token] = klass_or_proc.new(*resolved_dependencies)
      end
    else
      @resolved[token] = injection
    end
  end
end