(elbie 2): What does this warning mean?

I was unaware that one could run into problems using the object orientet syntax. I went and looked in the Perl Cookbook, but all I saw was a line that recommended the "procedural farmat for casual use", but it didn't really give me much of a reason for it.

I don't have access to Object Oriented Perl. What sort of dangers are you referring to?

elbieelbieelbie

Comment on (elbie 2): What does this warning mean?

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Re: (elbie 2): What does this warning mean? by davorg (Chancellor) on Aug 17, 2001 at 19:03 UTC
In the Cookbook, it's page 446 "A Warning on Indirect Object Notation" and in OOP it's pp98-101 "Another way to call a constructor". To summarise, there are two problems with it: The classname in `method CLASS` must be a bare symbol, a block or a scalar variable. It can't be just any old scalar expression. This can lead to surprising parsing. Perl needs to guess whether the `method` is, in fact, a method or a function. It can sometimes get this wrong. Particularly if your method has the same name as a function in your main package. In general it will work fine, but the times that it won't work are so difficult to keep a track of that it's best to never use it. There's no good reason not to use the alternative `CLASS->method` syntax, so I see it as a good habit to get into. -- <http://www.dave.org.uk> Perl Training in the UK <http://www.iterative-software.com>	[reply]

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Re: (elbie 2): What does this warning mean?
by davorg (Chancellor) on Aug 17, 2001 at 19:03 UTC

In the Cookbook, it's page 446 "A Warning on Indirect Object Notation" and in OOP it's pp98-101 "Another way to call a constructor".

To summarise, there are two problems with it:

The classname in method CLASS must be a bare symbol, a block or a scalar variable. It can't be just any old scalar expression. This can lead to surprising parsing.
Perl needs to guess whether the method is, in fact, a method or a function. It can sometimes get this wrong. Particularly if your method has the same name as a function in your main package.

In general it will work fine, but the times that it won't work are so difficult to keep a track of that it's best to never use it. There's no good reason not to use the alternative CLASS->method syntax, so I see it as a good habit to get into.

http://www.dave.org.uk

Perl Training in the UK <http://www.iterative-software.com>

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