# phpman > man > Devel::SelfStubber(3pm)

## NAME
    [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown) - generate stubs for a SelfLoading module

## SYNOPSIS
    To generate just the stubs:

        use [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown);
        [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown)->stub('MODULENAME','MY_LIB_DIR');

    or to generate the whole module with stubs inserted correctly

        use [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown);
        $[Devel::SelfStubber::JUST_STUBS](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber%3A%3AJUSTSTUBS/markdown)=0;
        [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown)->stub('MODULENAME','MY_LIB_DIR');

    MODULENAME is the Perl module name, e.g. [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown), NOT 'Devel/SelfStubber' or
    'Devel/SelfStubber.pm'.

    MY_LIB_DIR defaults to '.' if not present.

## DESCRIPTION
    [Devel::SelfStubber](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber/markdown) prints the stubs you need to put in the module before the __DATA__ token (or
    you can get it to print the entire module with stubs correctly placed). The stubs ensure that if
    a method is called, it will get loaded. They are needed specifically for inherited autoloaded
    methods.

    This is best explained using the following example:

    Assume four classes, A,B,C & D.

    A is the root class, B is a subclass of A, C is a subclass of B, and D is another subclass of A.

                            A
                           / \
                          B   D
                         /
                        C

    If D calls an autoloaded method 'foo' which is defined in class A, then the method is loaded
    into class A, then executed. If C then calls method 'foo', and that method was reimplemented in
    class B, but set to be autoloaded, then the lookup mechanism never gets to the AUTOLOAD
    mechanism in B because it first finds the method already loaded in A, and so erroneously uses
    that. If the method foo had been stubbed in B, then the lookup mechanism would have found the
    stub, and correctly loaded and used the sub from B.

    So, for classes and subclasses to have inheritance correctly work with autoloading, you need to
    ensure stubs are loaded.

    The SelfLoader can load stubs automatically at module initialization with the statement
    'SelfLoader->load_stubs()';, but you may wish to avoid having the stub loading overhead
    associated with your initialization (though note that the [SelfLoader::load_stubs](https://www.chedong.com/phpMan.php/perldoc/SelfLoader%3A%3Aloadstubs/markdown) method will be
    called sooner or later - at latest when the first sub is being autoloaded). In this case, you
    can put the sub stubs before the __DATA__ token. This can be done manually, but this module
    allows automatic generation of the stubs.

    By default it just prints the stubs, but you can set the global $[Devel::SelfStubber::JUST_STUBS](https://www.chedong.com/phpMan.php/perldoc/Devel%3A%3ASelfStubber%3A%3AJUSTSTUBS/markdown)
    to 0 and it will print out the entire module with the stubs positioned correctly.

    At the very least, this is useful to see what the SelfLoader thinks are stubs - in order to
    ensure future versions of the SelfStubber remain in step with the SelfLoader, the SelfStubber
    actually uses the SelfLoader to determine which stubs are needed.