Re: Weird variable scope problem

Hi John,

Pretty hard to know what's going on without looking at actual code, but it
could be some variation of this type of problem:
http://perl.apache.org/docs/1.0/guide/porting.html#Name_collisions_with_Modules_and_libs

You can easily run into trouble with code that either doesn't use package
names or exports things from use() calls.

> Is it possible for that kind of dynamic loading to result in multiple
lexical scopes for the same package?

No, Perl doesn't support that.

- Perrin


On Fri, Mar 25, 2016 at 4:23 PM, John Dunlap <[email protected]> wrote:

> They are initialized in my handler method, at the start of the request so
> they should be initialized at runtime. Basically, I have a singleton object
> which extends Class::Singleton which functions as an IOC container.
> However, because I have multiple virtual hosts and because the database
> connection is inside the IOC container, I have to have a separate object
> graph for each virtual host to prevent them from inadvertently talking to
> each other's databases. When I get an instance of the IOC container, I pass
> it the name of the site. Internally, it then maintains 2 lexically scoped
> variables; A hash, keyed by the name of the virtual host, and a scalar for
> storing the name of the current virtual host so that subsequent calls to
> the IOC container to get references to objects don't require a site name.
> This initialization happens at the start of every request to ensure that
> the right object graph is referenced when executing the request. However,
> in some older sections of the code base, when I attempt to references the
> IOC container these 2 lexically scoped variables are somehow empty, even
> though they were initialized at the start of the request, and then I get an
> error for attempting to call a function on an undefined value.
>
> I know that the code for some older areas of the application are loaded
> dynamically through evals and requires. Is it possible for that kind of
> dynamic loading to result in multiple lexical scopes for the same package?
>
> On Fri, Mar 25, 2016 at 3:58 PM, Perrin Harkins <[email protected]>
> wrote:
>
>> On Fri, Mar 25, 2016 at 10:11 AM, John Dunlap <[email protected]> wrote:
>>>
>>> Basically, I have a module which has a some lexically scoped variables
>>> in it. These variables are used by accessor methods in the package. The
>>> problem is that, if I use this module in certain parts of my application,
>>> these variables are mysteriously empty even though I am certain that I've
>>> already initialized them.
>>>
>>
>> How do you initialize them? In code that runs at compile-time in the same
>> module? In calls from httpd.conf or startup.pl? Is this an OO module
>> with a declared package name?
>>
>>
>>> Is there a way for a single perl interpreter to have multiple copies of
>>> a lexical variable?
>>>
>>
>> No, but keep in mind that mod_perl is running inside multiple httpd
>> processes and each one has a separate interpreter with unique copies of all
>> lexicals.
>>
>> - Perrin
>>
>>
>
>
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