7 our @EXPORT = qw(defer_sub undefer_sub);
13 my ($target, $maker, $undeferred_ref) = @{
14 $DEFERRED{$deferred}||return $deferred
16 ${$undeferred_ref} = my $made = $maker->();
17 if (defined($target)) {
18 no warnings 'redefine';
19 *{_getglob($target)} = $made;
21 push @{$DEFERRED{$made} = $DEFERRED{$deferred}}, $made;
27 $DEFERRED{$deferred||''};
31 my ($target, $maker) = @_;
35 goto &{$undeferred ||= undefer_sub($deferred_string)};
37 $deferred_string = "$deferred";
38 $DEFERRED{$deferred} = [ $target, $maker, \$undeferred ];
39 *{_getglob $target} = $deferred if defined($target);
47 Sub::Defer - defer generation of subroutines until they are first called
53 my $deferred = defer_sub 'Logger::time_since_first_log' => sub {
58 Logger->time_since_first_log; # returns 0 and replaces itself
59 Logger->time_since_first_log; # returns time - $t
63 These subroutines provide the user with a convenient way to defer creation of
64 subroutines and methods until they are first called.
70 my $coderef = defer_sub $name => sub { ... };
72 This subroutine returns a coderef that encapsulates the provided sub - when
73 it is first called, the provided sub is called and is -itself- expected to
74 return a subroutine which will be goto'ed to on subsequent calls.
76 If a name is provided, this also installs the sub as that name - and when
77 the subroutine is undeferred will re-install the final version for speed.
81 my $coderef = undefer_sub \&Foo::name;
83 If the passed coderef has been L<deferred|/defer_sub> this will "undefer" it.
84 If the passed coderef has not been deferred, this will just return it.
86 If this is confusing, take a look at the example in the L</SYNOPSIS>.