Re: Checking if a subroutine has been defined in a package...

Ok. I've been trying to do

Do something
    if defined &{"$package::$funcName"};
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and it's not working. Here's the situation:

In package A, I've got a function foo() which defines the subroutines, supposedly as needed.
In package B, which inherits (at some distance) from package A, I've got the definitions of various subroutines and the call to foo().

For some reason, the defined check isn't catching that the functions are supposed to be defined elsewhere. Why is that?

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Comment on Re: Checking if a subroutine has been defined in a package... Download Code

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Re: Re: Checking if a subroutine has been defined in a package... by pjf (Curate) on Oct 13, 2001 at 18:44 UTC
G'day dragonchild, What your code is doing is calling the subroutine "$package::$funcName", and checking if it returns a defined value. This is certainly not what you want to be doing, because if the subroutine does not exist, you end up with a fatal errror. If your subroutine does exist, you've just invoked it with no arguments, and it could return undef just to spite you anyway. Rather than calling the subroutine, you instead want to use globs to access perl's symbol table. This is described in my reply above. It also happens to be a bit faster than methods using can(), since inheritance is not checked. Cheers, Paul	[reply]

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Re: Re: Checking if a subroutine has been defined in a package...
by pjf (Curate) on Oct 13, 2001 at 18:44 UTC

dragonchild

What your code is doing is calling the subroutine "$package::$funcName", and checking if it returns a defined value. This is certainly not what you want to be doing, because if the subroutine does not exist, you end up with a fatal errror.

If your subroutine does exist, you've just invoked it with no arguments, and it could return undef just to spite you anyway.

Rather than calling the subroutine, you instead want to use globs to access perl's symbol table. This is described in my reply above. It also happens to be a bit faster than methods using can(), since inheritance is not checked.

Cheers,
Paul

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