7 our @EXPORT = qw(defer_sub undefer_sub);
13 my ($target, $maker, $undeferred_ref) = @{
14 $DEFERRED{$deferred}||return $deferred
16 ${$undeferred_ref} = my $made = $maker->();
18 # make sure the method slot has not changed since deferral time
19 if (defined($target) && $deferred eq *{_getglob($target)}{CODE}||'') {
20 no warnings 'redefine';
22 # I believe $maker already evals with the right package/name, so that
23 # _install_coderef calls are not necessary --ribasushi
24 *{_getglob($target)} = $made;
26 push @{$DEFERRED{$made} = $DEFERRED{$deferred}}, $made;
33 $DEFERRED{$deferred||''};
37 my ($target, $maker) = @_;
41 goto &{$undeferred ||= undefer_sub($deferred_string)};
43 $deferred_string = "$deferred";
44 $DEFERRED{$deferred} = [ $target, $maker, \$undeferred ];
45 _install_coderef $target => $deferred if defined $target;
53 Sub::Defer - defer generation of subroutines until they are first called
59 my $deferred = defer_sub 'Logger::time_since_first_log' => sub {
64 Logger->time_since_first_log; # returns 0 and replaces itself
65 Logger->time_since_first_log; # returns time - $t
69 These subroutines provide the user with a convenient way to defer creation of
70 subroutines and methods until they are first called.
76 my $coderef = defer_sub $name => sub { ... };
78 This subroutine returns a coderef that encapsulates the provided sub - when
79 it is first called, the provided sub is called and is -itself- expected to
80 return a subroutine which will be goto'ed to on subsequent calls.
82 If a name is provided, this also installs the sub as that name - and when
83 the subroutine is undeferred will re-install the final version for speed.
87 my $coderef = undefer_sub \&Foo::name;
89 If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it.
90 If the passed coderef has not been deferred, this will just return it.
92 If this is confusing, take a look at the example in the L</SYNOPSIS>.