GAE：模型失去父级>子关系的跟踪

问题描述

我在google app引擎数据存储中遇到了一个非常奇怪的Entity关系问题。我在一个Python / GAE webapp（学习练习），完整的代码可以在。

I'm having what seems like a very strange problem with an Entity relationship in the google app engine data store. I'm work on a Python/GAE webapp (learning exercise), the full code to which can be found on sourceforge.

• 我有2个型号：
  
  
  
  • - 搜索字词和（间接）照片列表
  
  
  • - 有关照片的信息，
  
  
  
  • 我有一个获取过程，可以创建图库并向其中添加照片
  
  
  • 我有一个从数据存储区读取图库的页面，并使用该图库实例的.photos属性来获取其中的照片列表。
  
  
  • I have 2 models:
    • Gallery - a search term and (indirectly) a list of photos
    • Photo - information about a photo, plus the gallery it belongs to (collection_index='photos')

    现在这是奇怪的部分来的地方... 如果我更改一个文件（我测试过的任何文件），或者只是更新文件的时间戳例如，如果我尝试加载：

    Now this is where the weird part comes in... If I change a file (any file I've tested on) or even just update the timestamp of the file (ie, so it gets reloaded)... the ".photos" attribute of galleries starts failing. For example, if I try to load the page for the "flowers" gallery:

     c $  $  >类，应用程序引擎重新加载代码...因为它的定义被正在修改的文件无效

  
  
  • 因为它不知道它需要照片类，它不会加载该文件，因此 Gallery 类的新实例没有应该

  My first solution was to add a dependency on the Photo file in the Gallery file.

  from app.models.photo import Photo
  

  这样的问题是在两个文件之间创建一个循环依赖（因为照片已经需要知道图库以获得它们的列表）。虽然它工作，我被告知Python有问题与循环依赖，这可能不是一件好事;

  The problem with this is that it creates a circular dependency between the two files (since Photo already needs to know about Gallery in order to have a list of them). While it worked, I was told that Python has "problems" with circular dependencies, and it's probably not a good thing to do; it may come back to bite me later.

  我解决的解决方案是将__init.py 文件所讨论的包包括两个文件的依赖关系。因此，任何时候只需要其中一个文件即可加载。

  The solution I wound up going with was to have the __init.py file for the package in question include a dependency for both files. As such, any time either one of the files is needed, both will be loaded.

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