Re: How do you use/create subroutine attributes?

Well, it all depends on what kind of magic you want to happen.

I am pretty sure that MODIFY_CODE_ATTRIBUTES will run in the BEGIN phase of the perl compiler. And the $code passed to you is usually a stub, and not the true subroutine that you will eventually have (however it's ref address will stay the same, so you can use that). What Catalyst does is to store the code-ref address along with the list of attributes it had for it, then when Catalyst is initialized (sometime during runtime presumably) it matches code-refs to attributes (using attribute::get() which calls FETCH_CODE_ATTRIBUTES) and does magic then. Attribute::Handlers does similar stuff, but it uses the INIT phase of the perl compiler to do it's dirty work.

In general subroutine attributes are an unwieldy beast with a really bad interface. They are especially tricky when it comes to CODE references. But then again, this is my experience, and your mileage may vary.

-stvn

Comment on Re: How do you use/create subroutine attributes?

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Re^2: How do you use/create subroutine attributes? by xdg (Monsignor) on Mar 17, 2006 at 20:22 UTC
Supposedly, Attribute::Handlers can act at any compilation stage, though the default is CHECK, as that's a point at which most things are compiled and in place. The big limitation is that the name in the symbol table for a subroutine isn't set at the time attributes are first processed -- only the package name and the code reference (that later gets stored in the symbol table) are available. Technically, the `MODIFY__ATTRIBUTES` from `Attribute::Handlers` runs immediately during compilation (like a BEGIN block) -- but by default, `Attribute::Handlers` just stores everything it can about the call at that point. Later, during CHECK, it calls the appropriate handlers on the previously stored information, which, among other things, allows looking up the name of the coderef in the symbol table to find the name of a subroutine. -xdg Code written by xdg and posted on PerlMonks is public domain. It is provided as is* with no warranties, express or implied, of any kind. Posted code may not have been tested. Use of posted code is at your own risk.	[reply] [d/l] [select]

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Re^2: How do you use/create subroutine attributes?
by xdg (Monsignor) on Mar 17, 2006 at 20:22 UTC

Supposedly, Attribute::Handlers can act at any compilation stage, though the default is CHECK, as that's a point at which most things are compiled and in place. The big limitation is that the name in the symbol table for a subroutine isn't set at the time attributes are first processed -- only the package name and the code reference (that later gets stored in the symbol table) are available.

Technically, the MODIFY_*_ATTRIBUTES from Attribute::Handlers runs immediately during compilation (like a BEGIN block) -- but by default, Attribute::Handlers just stores everything it can about the call at that point. Later, during CHECK, it calls the appropriate handlers on the previously stored information, which, among other things, allows looking up the name of the coderef in the symbol table to find the name of a subroutine.

-xdg

Code written by xdg and posted on PerlMonks is public domain. It is provided as is with no warranties, express or implied, of any kind. Posted code may not have been tested. Use of posted code is at your own risk.

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