Author: larry
Date: Tue Nov 7 09:31:45 2006
New Revision: 13473
Modified:
doc/trunk/design/syn/S12.pod
Log:
BUILD submethods attempt to discourage method calls on inconsistent data.
Modified: doc/trunk/design/syn/S12.pod
==============================================================================
--- doc/trunk/design/syn/S12.pod (original)
+++ doc/trunk/design/syn/S12.pod Tue Nov 7 09:31:45 2006
@@ -12,9 +12,9 @@
Maintainer: Larry Wall <[EMAIL PROTECTED]>
Date: 27 Oct 2004
- Last Modified: 6 Nov 2006
+ Last Modified: 7 Nov 2006
Number: 12
- Version: 31
+ Version: 32
=head1 Overview
@@ -451,6 +451,20 @@
internal storage location via C<$!foo> should generally be restricted
to submethods. Ordinary methods should stick to the C<$.foo> form.
+In fact, within submethods, use of the C<$.foo> form on attributes
+that are available as C<$!foo> (that is, that are declared directly
+by this class) is illegal and produces a dire compile-time warning
+(which may be suppressed). Within a submethod the C<$.foo> form may
+only be used on attributes from parent classes, because only the parent
+classes' part of the object is guaranteed to be in a consistent state
+(because C<BUILDALL> call's the parent classes' C<BUILD> routines
+first). If you attempt to get around this by declaring C<BUILD> as
+a method rather than a submethod, that will also be flagged as a dire
+(but suppressible) compile-time warning. (It is I<possible> to define
+an inheritable C<BUILD> routine if you have access to all the metadata
+for the current class, but it's not easy, and it certainly doesn't
+happen by accident just because you change C<submethod> to C<method>.)
+
Because C<$.foo>, C<@.foo>, C<%.foo>, C<&.foo> are just shorthands of
C<self.foo> with different contexts, the class does not need to declare
C<has $.foo> as an attribute -- a C<method foo> declaration can work
@@ -481,10 +495,13 @@
has $.r = INIT { rand };
has $.r = ENTER { rand };
has $.r = FIRST { rand };
+ has $.r = constant $myrand = rand;
-When it is called at BUILD time, the topic of the implicit closure
+When it is called at C<BUILD> time, the topic of the implicit closure
will be the attribute being initialized, while "self" refers to the
-entire object being initialized.
+entire object being initialized. The closure will be called at the
+end of the C<BUILD> only if the attribute is not otherwise initialized
+in either the signature or the body of the C<BUILD>.
Class attributes are declared with either C<my> or C<our>. The only
difference from ordinary C<my> or C<our> variables is that an accessor
