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Пакет: perl-Import-Into
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Текущая версия: 1.002005-alt1
Время сборки: 11 октября 2015, 18:38 ( 445.7 недели назад )
Размер архива: 15.54 Kb
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Лицензия: Artistic
О пакете: import packages into other packages
Описание:
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Время сборки: 11 октября 2015, 18:38 ( 445.7 недели назад )
Размер архива: 15.54 Kb
Домашняя страница: http://search.cpan.org/CPAN/authors/id/http://s…
Лицензия: Artistic
О пакете: import packages into other packages
Описание:
Writing exporters is a pain. Some use the Exporter manpage, some use the Sub::Exporter manpage,
some use the Moose::Exporter manpage, some use the Exporter::Declare manpage ... and some things
are pragmas.
If you want to re-export other things, you have to know which is which.
the Exporter manpage subclasses provide export_to_level, but if they overrode their
import method all bets are off. the Sub::Exporter manpage provides an into parameter
but figuring out something used it isn't trivial. Pragmas need to have
their `import' method called directly since they affect the current unit of
compilation.
It's ... annoying.
However, there is an approach that actually works for all of these types.
eval "package $target; use $thing;"
will work for anything checking caller, which is everything except pragmas.
But it doesn't work for pragmas - pragmas need:
$thing->import;
because they're designed to affect the code currently being compiled - so
within an eval, that's the scope of the eval itself, not the module that
just `use'd you - so
sub import {
eval "use strict;"
}
doesn't do what you wanted, but
sub import {
strict->import;
}
will apply the strict manpage to the calling file correctly.
Of course, now you have two new problems - first, that you still need to
know if something's a pragma, and second that you can't use either of
these approaches alone on something like the Moose manpage or the Moo manpage that's both
an exporter and a pragma.
So, the complete solution is:
my $sub = eval "package $target; sub { shift->import(\@_) }";
$sub->($thing, @import_args);
which means that import is called from the right place for pragmas to take
effect, and from the right package for caller checking to work - and so
behaves correctly for all types of exporter, for pragmas, and for hybrids.
Remembering all this, however, is excessively irritating. So I wrote a module
so I didn't have to anymore. Loading the Import::Into manpage creates a global method
`import::into' which you can call on any package to import it into another
package. So now you can simply write:
use Import::Into;
$thing->import::into($target, @import_args);
This works because of how perl resolves method calls - a call to a simple
method name is resolved against the package of the class or object, so
$thing->method_name(@args);
is roughly equivalent to:
my $code_ref = $thing->can('method_name');
$code_ref->($thing, @args);
while if a `::' is found, the lookup is made relative to the package name
(i.e. everything before the last `::') so
$thing->Package::Name::method_name(@args);
is roughly equivalent to:
my $code_ref = Package::Name->can('method_name');
$code_ref->($thing, @args);
So since the Import::Into manpage defines a method `into' in package `import'
the syntax reliably calls that.
For more craziness of this order, have a look at the article I wrote at
http://shadow.cat/blog/matt-s-trout/madness-wit… which covers
coderef abuse and the `${\...}' syntax.
Final note: You do still need to ensure that you already loaded `$thing' - if
you're receiving this from a parameter, I recommend using the Module::Runtime manpage:
use Import::Into;
use Module::Runtime qw(use_module);
use_module($thing)->import::into($target, @import_args);
And that's it.
Текущий майнтейнер: Igor Vlasenko some use the Moose::Exporter manpage, some use the Exporter::Declare manpage ... and some things
are pragmas.
If you want to re-export other things, you have to know which is which.
the Exporter manpage subclasses provide export_to_level, but if they overrode their
import method all bets are off. the Sub::Exporter manpage provides an into parameter
but figuring out something used it isn't trivial. Pragmas need to have
their `import' method called directly since they affect the current unit of
compilation.
It's ... annoying.
However, there is an approach that actually works for all of these types.
eval "package $target; use $thing;"
will work for anything checking caller, which is everything except pragmas.
But it doesn't work for pragmas - pragmas need:
$thing->import;
because they're designed to affect the code currently being compiled - so
within an eval, that's the scope of the eval itself, not the module that
just `use'd you - so
sub import {
eval "use strict;"
}
doesn't do what you wanted, but
sub import {
strict->import;
}
will apply the strict manpage to the calling file correctly.
Of course, now you have two new problems - first, that you still need to
know if something's a pragma, and second that you can't use either of
these approaches alone on something like the Moose manpage or the Moo manpage that's both
an exporter and a pragma.
So, the complete solution is:
my $sub = eval "package $target; sub { shift->import(\@_) }";
$sub->($thing, @import_args);
which means that import is called from the right place for pragmas to take
effect, and from the right package for caller checking to work - and so
behaves correctly for all types of exporter, for pragmas, and for hybrids.
Remembering all this, however, is excessively irritating. So I wrote a module
so I didn't have to anymore. Loading the Import::Into manpage creates a global method
`import::into' which you can call on any package to import it into another
package. So now you can simply write:
use Import::Into;
$thing->import::into($target, @import_args);
This works because of how perl resolves method calls - a call to a simple
method name is resolved against the package of the class or object, so
$thing->method_name(@args);
is roughly equivalent to:
my $code_ref = $thing->can('method_name');
$code_ref->($thing, @args);
while if a `::' is found, the lookup is made relative to the package name
(i.e. everything before the last `::') so
$thing->Package::Name::method_name(@args);
is roughly equivalent to:
my $code_ref = Package::Name->can('method_name');
$code_ref->($thing, @args);
So since the Import::Into manpage defines a method `into' in package `import'
the syntax reliably calls that.
For more craziness of this order, have a look at the article I wrote at
http://shadow.cat/blog/matt-s-trout/madness-wit… which covers
coderef abuse and the `${\...}' syntax.
Final note: You do still need to ensure that you already loaded `$thing' - if
you're receiving this from a parameter, I recommend using the Module::Runtime manpage:
use Import::Into;
use Module::Runtime qw(use_module);
use_module($thing)->import::into($target, @import_args);
And that's it.
Список всех майнтейнеров, принимавших участие
в данной и/или предыдущих сборках пакета: Список rpm-пакетов, предоставляемый данным srpm-пакетом:
- perl-Import-Into