循环依赖与自动加载

Question

我有一个超类锻炼：

class Workout < ActiveRecord::Base
  SUBCLASSES = [WeeklyWorkout, DailyWorkout, OneTimeWorkout]
  (...)
end

我需要子类列表。每个子类都是这样的：

class WeeklyWorkout < Workout
   (...)
end

所以，当我加载锻炼课程时，一切正常。但是当我尝试加载任何子类（没有先加载 Workout 类）时，循环依赖存在问题。例如：

irb(main):062:0> 每周锻炼 RuntimeError：自动加载常量 WeeklyWorkout 时检测到循环依赖 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:460:in `load_missing_constant' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:183:in `const_missing' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:494:in `load_missing_constant' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:183:in `const_missing' 来自 /home/pablo/rails/tobefit/app/models/workout.rb:2:in `' 来自 /home/pablo/rails/tobefit/app/models/workout.rb:1:in `' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `load' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `block in load_file' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:615:in `new_constants_in' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:422:in `load_file' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:323:in `require_or_load' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:462:in `load_missing_constant' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:183:in `const_missing' 来自/home/pablo/rails/tobefit/app/models/workouts/weekly_workout.rb:1:in `' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `load' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:423:in `block in load_file' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:615:in `new_constants_in' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:422:in `load_file' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:323:in `require_or_load' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:462:in `load_missing_constant' 来自 /var/lib/gems/1.9.1/gems/activesupport-4.0.0/lib/active_support/dependencies.rb:183:in `const_missing' 来自 (irb):62 来自 /var/lib/gems/1.9.1/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start' 来自 /var/lib/gems/1.9.1/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start' 来自 /var/lib/gems/1.9.1/gems/railties-4.0.0/lib/rails/commands.rb:64:in `' 从 bin/rails:4:in `require' 从 bin/rails:4:in `'

我知道为什么会出现问题。但我不知道如何解决它。有谁知道如何设计这个来解决这个问题？

Answer 1

当你写作时：

SUBCLASSES = [WeeklyWorkout, DailyWorkout, OneTimeWorkout]

它会自动加载各种文件。 （我想你知道这一点。）

避免该问题的一种方法是使用符号：

SUBCLASSES = [:WeeklyWorkout, :DailyWorkout, :OneTimeWorkout]

然后，当您访问 SUBCLASSES 的元素时，请使用 const_get。这将防止子类文件与父类文件一起自动加载。