```ruby
require 'lazy_const'

class FeatureDefinitions
  extend LazyConst

  def self.define_feature(name, opts = {}, &block)
    lazy_const(name){ new(opts, &block) }
  end

  def initialize(opts = {}, &block)
    @opts = opts
    @proc = block.to_proc
  end

  def self.context=(context)
    @@context = context
  end

  def enabled?
    args = @opts[:using].map { |sym| @@context.public_send(sym) }
    @proc.call(*args)
  end

end
```

Refactor out instance/class variable access, add block mode
user
```ruby
require 'lazy_const'

class FeatureDefinitions
  extend LazyConst
  attr_reader :opts, :test_proc

  def self.define_feature(name, opts = {}, &block)
    lazy_const(name){ new(opts, block.to_proc) }
  end

  def initialize(opts, proc)
    @opts = opts
    @test_proc = proc
  end

  def self.context=(context)
    @@context = context
  end

  def context
    @@context
  end

  def enabled?(&block)
    args = opts[:using].map { |sym| context.public_send(sym) }
    test_proc.call(*args).tap do |verdict|
      yield if block_given? and verdict
    end
  end
end
```
assistant