ruby-on-rails – Ruby / Rails依赖注入

我试图了解 Ruby / Rails中的依赖注入.如何使用依赖注入删除Builders对Saw的显式引用？

class Builder
  attr_reader :saw

  def saw
    @saw ||= Saw.new(4)
  end

  def cut_wood
    Saw.saw
  end
end

class Saw
  attr_reader :blades

  def initialize(blades)
    @blades = blades
  end

  def saw
    # do something
  end
end

解决方法

将Saw的初始化移动到默认参数.

class Builder   
  def saw(saw = Saw.new(4))
    @saw = saw
  end

  def cut_wood
    Saw.saw
  end
end

Builder#saw现在支持依赖注入.

请记住删除attr_reader：从您的代码中查看,因为它被您的自定义阅读器覆盖.