[SQLObject] Re: id, str(id) and duplicate objects in the cache

[Edmund L. <el...@in...>]

Matt Goodall wrote:

 > The problem is probably best demonstrated by (untested) example with a
 > description of what happens inside SQLObject's caches:
 >
 >   id = Obj.new(col1='a', col2='b')
 >   # added to cache with key == int(1)
 >
 >   o = Obj(id)
 >   # found in cache with key == int(1)
 >
 >   o = Obj(str(id)) # note the cast to a string
 >   # reads from database, adds to cache with key == str(1)
 >   # Eek, two objects now in cache!


Argh! This problem is very easy to run into. For example, if you pass an 
object ID to another page as a field variable, then it is all too easy 
to forget that you have to cast the value back to an integer before 
using it.

Example:

 From one servlet that has fiddled with obj1 = MyObject(3), redirect to 
another page with a URL like http://my.url/Index?id=3

Then in the Index.py servlet:
id = self.request().field("id")
obj2 = MyObject(id)

Oops! obj1 and obj2 aren't the same objects anymore! It's just too easy 
to do this!!

...Edmund.