如何在关注点中定义 state_machine?

问题描述

我正在尝试将一些重复的逻辑分解为 关注.部分重复逻辑是 state_machine.

I am trying to factor out some duplicated logic into a concern. Part of the duplicated logic is a state_machine.

经过简化，Database、Site、SftpUser 等包含以下内容:

Simplified, the Database, Site, SftpUser and more contain, amongst others, this:

class Database < ActiveRecord::Base
  # ...
  state_machine :deploy_state, initial: :halted do
    state :pending
  end
end

我正在尝试将其重构为一个问题:

I'm attempting to refactor this into a concern:

module Deployable
  extend ActiveSupport::Concern

  included do
    state_machine :deploy_state, initial: :halted do
      state :pending
    end
  end
end

# Tested with:
class DeployableDouble < ActiveRecord::Base
  extend Deployable
end

describe DeployableDouble do
  let(:subject) { DeployableDouble.new }

  it "should have default state halted" do
    subject.deploy_state.must_equal "halted"
  end
end

然而，这不是在关注中实现state_machine的正确方法，因为这会导致:NoMethodError: undefined method 'deploy_state' for <DeployableDouble:0xb9831f8>.这表明 Double 根本没有获得分配的状态机.

However, this is not the correct way to implement a state_machnine in a concern, because this results in: NoMethodError: undefined method 'deploy_state' for <DeployableDouble:0xb9831f8>. Which indicates that the Double did not get a statemachine assigned at all.

included do 实际上是实现此功能的正确回调吗?它可能是 state_machine 的问题，它需要一个 ActiveRecord::Base 的子类吗?我没有得到的东西?我对关注的概念还很陌生.

Is the included do actually the right callback to implement this? Is it maybe an issue with state_machine, it needing a subclass of ActiveRecord::Base or so? Something I'm not getting? I am pretty new to the concept of Concerns.

推荐答案

好的.我真的觉得自己很蠢.不应该extend一个带有模块的类，而是include那个模块.很明显.

Okay. I am feeling really stupid. One should not extend a class with a module, but include that module. Obviously.

# Tested with:
class DeployableDouble
  include Deployable
end

一旦写完，你就监督其中的一件事情.此外，不需要扩展 ActiveRecord::Base，因为 state_machine 只是普通的旧 Ruby 并且适用于通用 Ruby 对象.

One of these things that you oversee once written. Also, extending the ActiveRecord::Base is not needed, since state_machine is just plain old Ruby and works on a generic Ruby Object.

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