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';
21 *{_getglob($target)} = $made;
23 push @{$DEFERRED{$made} = $DEFERRED{$deferred}}, $made;
30 $DEFERRED{$deferred||''};
34 my ($target, $maker) = @_;
38 goto &{$undeferred ||= undefer_sub($deferred_string)};
40 $deferred_string = "$deferred";
41 $DEFERRED{$deferred} = [ $target, $maker, \$undeferred ];
42 *{_getglob $target} = $deferred if defined($target);
50 Sub::Defer - defer generation of subroutines until they are first called
56 my $deferred = defer_sub 'Logger::time_since_first_log' => sub {
61 Logger->time_since_first_log; # returns 0 and replaces itself
62 Logger->time_since_first_log; # returns time - $t
66 These subroutines provide the user with a convenient way to defer creation of
67 subroutines and methods until they are first called.
73 my $coderef = defer_sub $name => sub { ... };
75 This subroutine returns a coderef that encapsulates the provided sub - when
76 it is first called, the provided sub is called and is -itself- expected to
77 return a subroutine which will be goto'ed to on subsequent calls.
79 If a name is provided, this also installs the sub as that name - and when
80 the subroutine is undeferred will re-install the final version for speed.
84 my $coderef = undefer_sub \&Foo::name;
86 If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it.
87 If the passed coderef has not been deferred, this will just return it.
89 If this is confusing, take a look at the example in the L</SYNOPSIS>.