Ruby on rails 为关联（未定义的方法'relation_delegate_class'；）截取模型常量

我有一个

课程

模型，它与

权限

模型关联：

app/models/lesson.rb

：

class Lesson < ActiveRecord::Base
  has_many :permissions, :class_name => 'Permission', as: :permissible, dependent: :destroy
  ...

  def create_permissions
    Permission::DEFAULTS[:lesson].each do |action, value|
      ..
    end
  end

class Permission < ActiveRecord::Base
  DEFAULTS = {
    lesson: {some_more_action: 15}
  }

  belongs_to :permissible, polymorphic: true
end

require 'rails_helper'

RSpec.describe Lesson, :type => :model do
  describe "#create_permissions" do
    let!(:lesson) { FactoryGirl.build_stubbed :lesson }

    before(:each) do
      stub_const('Permission::DEFAULTS', {lesson: {some_action: 5}})
    end

    it 'should create permissions' do
      lesson.create_permissions

      permission = lesson.permissions.first

      ...
    end
  end
end

我使用RSpec

stub\u const

方法：

spec/models/lesson\u spec.rb

：

class Lesson < ActiveRecord::Base
  has_many :permissions, :class_name => 'Permission', as: :permissible, dependent: :destroy
  ...

  def create_permissions
    Permission::DEFAULTS[:lesson].each do |action, value|
      ..
    end
  end

class Permission < ActiveRecord::Base
  DEFAULTS = {
    lesson: {some_more_action: 15}
  }

  belongs_to :permissible, polymorphic: true
end

require 'rails_helper'

RSpec.describe Lesson, :type => :model do
  describe "#create_permissions" do
    let!(:lesson) { FactoryGirl.build_stubbed :lesson }

    before(:each) do
      stub_const('Permission::DEFAULTS', {lesson: {some_action: 5}})
    end

    it 'should create permissions' do
      lesson.create_permissions

      permission = lesson.permissions.first

      ...
    end
  end
end

但规范失败，出现错误：

Failure/Error: permission = lesson.permissions.first
NoMethodError:
  undefined method `relation_delegate_class' for Permission:Module
 # /home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active_record/relation/delegation.rb:112:in `relation_class_for'
 # /home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active_record/relation/delegation.rb:106:in `create'
 # /home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active_record/associations/collection_association.rb:41:in `reader'
 # /home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active_record/associations/builder/association.rb:115:in `permissions'
 # ./spec/models/lesson_spec.rb:285:in `block (3 levels) in <top (required)>'

失败/错误：权限=lesson.permissions.first
命名错误：
权限：模块的未定义方法“关系\委托\类”
#/home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active\u record/relation/delegation.rb:112:在“relation\u class\u for”中
#/home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active\u record/relation/delegation.rb:106:在“创建”中
#/home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active\u record/associations/collection\u association.rb:41:在“reader”中
#/home/install/.rvm/gems/ruby-2.1.4/gems/activerecord-4.2.3/lib/active\u record/associations/builder/association.rb:115:在“权限”中
#./spec/models/lesson_spec.rb:285:in'block（3层）in'

看起来，

权限

不再是与课程模型关联的rails。有没有关于如何获得这一轮的想法

---

Gem版本：

rspec-3.3.0

，

rspec-rails-3.3.3

，

rails-4.2.3

，我遇到的唯一选择就是在一个示例中显式设置常量：

before(:each) do
  Permission::DEFAULTS = {lesson: {some_action: 5}}
end

但我觉得这不是个好主意。它还提出了一些警告：

spec/models/lesson_spec.rb:279: warning: already initialized constant Permission::DEFAULTS
app/models/permission.rb:2: warning: previous definition of DEFAULTS was here

---

请仔细查看此错误消息：

NoMethodError:
  undefined method `relation_delegate_class' for Permission:Module

权限

在这里被描述为

模块

，而不是

类

。我认为这是因为在存根嵌套常量时，

权限

类尚未加载，RSpec也必须通过

模块

存根它

请尝试以下解决方法：

before(:each) do
  Permission # load real ActiveRecord Permission class
  stub_const('Permission::DEFAULTS', {lesson: {some_action: 5}})
end

编辑：作为旁注，我不认为将嵌套常量公开给其他类是一个好主意，您对常量几乎没有控制权（只是更改名称或值），并且您不能像使用方法那样包装任何行为。我建议使用方法将public

Permission

的API更改为，这样也更容易存根：

class Permission < ActiveRecord::Base
  DEFAULTS = {
    lesson: {some_more_action: 15}
  }

  def self.defaults
    DEFAULTS
  end    
end

---

很成功！有类似想法，但不知道这会导致RSpec改变行为。非常感谢。将在一个方法中结束它。