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## -------------------------------------------------------------------------------- |
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## $Id: Bridge.pm,v 1.12 2003/05/13 08:39:22 joko Exp $ |
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## -------------------------------------------------------------------------------- |
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## $Log: Bridge.pm,v $ |
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## Revision 1.12 2003/05/13 08:39:22 joko |
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## autocalling constructor after instantiation |
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## added pod documentation |
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## |
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## Revision 1.11 2003/02/21 08:38:21 joko |
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## + additional checks |
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## + raising exceptions |
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## |
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## Revision 1.10 2003/02/20 20:50:32 joko |
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## + small exception handling: now inheriting from little Exception object |
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## |
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## Revision 1.9 2003/02/18 18:35:30 joko |
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## + encapsulated/abstracted some more functionality: sub load_single |
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## |
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## Revision 1.8 2003/02/14 14:20:05 joko |
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## + modified mixin behaviour |
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## |
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## Revision 1.7 2003/02/11 10:34:19 joko |
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## + loaded module may now lack 'mixin::with' declaration |
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## + this gets us the possibility to load modules from any perl namespace |
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## + enabled this mechanism |
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## |
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## Revision 1.6 2003/02/09 16:22:51 joko |
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## + pseudo constructor mechanism via options |
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## |
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## Revision 1.5 2003/01/31 01:19:50 root |
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## + fixed: doesn't need Log::Dispatch any more, but uses it if available |
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## |
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## Revision 1.4 2003/01/20 16:55:15 joko |
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## + sub mixinPackage |
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## + sub include |
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## |
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## Revision 1.3 2002/12/16 19:57:12 joko |
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## + sub unload |
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## |
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## Revision 1.2 2002/12/15 02:06:15 joko |
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## + feature to be able to specify module in non-perl-style when loading plugins: e.g. $process->load('Setup/Storage') |
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## |
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## Revision 1.1 2002/12/13 21:46:29 joko |
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## + initial check-in |
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## |
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## -------------------------------------------------------------------------------- |
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|
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|
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package DesignPattern::Bridge; |
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|
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use strict; |
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use warnings; |
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|
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use base qw( |
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DesignPattern::Object |
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DesignPattern::Exception |
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); |
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|
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|
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use Data::Dumper; |
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|
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=pod |
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|
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=head1 NAME |
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|
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DesignPattern::Bridge |
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|
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|
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=head1 DESCRIPTION |
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|
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This acts as a generic backplane for plugins using "Mix-in inheritance". |
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|
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|
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=head2 BACKGROUND |
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|
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Mix-in inheritance |
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Please visit [http://citeseer.nj.nec.com/bracha90mixinbased.html]. |
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|
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[...] |
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Abstract: The diverse inheritance mechanisms provided by Smalltalk, Beta, |
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and CLOS are interpreted as different uses of a single underlying construct. |
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Smalltalk and Beta differ primarily in the direction of class hierarchy growth. |
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These inheritance mechanisms are subsumed in a new inheritance model |
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based on composition of mixins, or abstract subclasses. This form of |
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inheritance can also encode a CLOS multiple-inheritance hierarchy, although |
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changes to the encoded hierarchy that would violate... (Update) |
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[...] |
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|
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...level, and can naturally span component boundaries. Jiazzi supports |
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the composition of class extending components; e.g. mixins [1]. Mixins |
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and cyclic component linking can be combined into an open class pattern, |
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which allows independent features that cross cut class... |
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|
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=head3 History of "mixins" |
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|
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=head4 G. Bracha, W. Cook. Mixin-based inheritance. |
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|
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G. Bracha and W. Cook, "Mixin-Based Inheritance", ECOOP/OOPSLA 1990, 303-311. |
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G. Bracha, W. Cook. Mixin-based inheritance. In OOPSLA/ECOOP '90 Conference Proceedings. ACM SIGPLAN Notices 25, 10 (Oct. 1990). |
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|
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@inproceedings{ bracha90mixinbased, |
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author = "Gilad Bracha and William Cook", |
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title = "Mixin-Based Inheritance", |
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booktitle = "Proceedings of the Conference on Object-Oriented Programming: Systems, Languages, and Applications / Proceedings of the European Conference on Object-Oriented Programming", |
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publisher = "ACM Press", |
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address = "Ottawa, Canada", |
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editor = "Norman Meyrowitz", |
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pages = "303--311", |
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year = "1990", |
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url = "citeseer.nj.nec.com/bracha90mixinbased.html" } |
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|
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=head4 D. Duggan and C. Sourelis. Mixin modules. |
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|
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http://users.hol.gr/~csourelis/thesis.html |
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|
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@misc{ duggan96mixin, |
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author = "D. Duggan and C. Sourelis", |
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title = "Mixin modules", |
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text = "D. Duggan and C. Sourelis. Mixin modules. In Intl. Conf. on Functional |
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Programming, Philadelphia, May 1996. ACM Press.", |
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year = "1996", |
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url = "citeseer.nj.nec.com/sourelis95mixin.html" } |
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|
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=head4 Google on your own: |
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|
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http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=mix-in+inheritance |
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http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&q=Moo86+mixins |
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|
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|
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=head3 Discussion |
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|
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http://citeseer.nj.nec.com/context/6117/0 |
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|
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=head2 References |
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|
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The Jigsaw Framework: |
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http://citeseer.nj.nec.com/bracha92programming.html |
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|
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http://citeseer.nj.nec.com/114070.html |
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http://citeseer.nj.nec.com/445396.html |
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http://citeseer.nj.nec.com/tichelaar97coordination.html |
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http://citeseer.nj.nec.com/meijler98beyond.html |
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|
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http://citeseer.nj.nec.com/89291.html |
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http://citeseer.nj.nec.com/sousa91runtime.html |
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http://citeseer.nj.nec.com/banavar95application.html |
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http://citeseer.nj.nec.com/sourelis95mixin.html |
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http://citeseer.nj.nec.com/hirschowitz02mixin.html |
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|
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Java: http://csis.pace.edu/~bergin/patterns/multipleinheritance.html |
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C++: http://www.oofile.com.au/oofdoc/samples/ooftst19.htm |
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|
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=head3 Related |
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|
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http://citeseer.nj.nec.com/nrelated/6117/23339 |
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|
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|
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=head3 Traits - Composable Units of Behavior |
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|
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via: http://citeseer.nj.nec.com/context/22076/0 |
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|
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Traits: Composable Units of Behavior - Nathanael Schrli Stphane (Correct) |
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....is not expressive enough to factor out common features (i.e. instance |
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variables and methods) shared by classes in a complex hierarchy. As a |
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consequence, language designers have proposed various forms of multiple |
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inheritance [Mey88] Kee89] Str86] as well as other mechanisms, such as |
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mixins [Moo86] BC90] FKF98] that allow classes to be composed incrementally |
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from sets of features. Despite the passage of nearly twenty years, neither |
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multiple inheritance nor mixins have achieved wide acceptance [Tai96] |
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Summarizing Alan Snyder s contribution to the inheritance panel discussion |
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at OOPSLA .... |
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|
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....complete. But as a unit of reuse, a class should be small. These properties |
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often conflict. Furthermore, the role of classes as instance generators requires |
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that each class have a unique place in the class hierarchy, whereas units of |
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reuse should be applicable at arbitrary places. Moon s Flavors [Moo86] were |
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an early attempt to address this problem: Flavors are small, not necessarily |
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complete, and they can be mixed in at arbitrary places in the class hierarchy. |
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More sophisticated notions of mixins were subsequently developed by Bracha |
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and Cook [BC90] and Flatt, Krishnamurthi and Felleisen .... |
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|
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David A. Moon. Object-oriented programming with flavors. In Proceedings |
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OOPSLA '86, ACM SIGPLAN Notices, pages 1--8, November 1986. |
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Published as Proceedings OOPSLA '86, ACM SIGPLAN Notices, volume 21, number 11. |
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|
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|
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from: http://citeseer.nj.nec.com/566972.html |
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|
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Abstract: Inheritance is the fundamental reuse mechanism in object-oriented |
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programming languages; its most prominent variants are single inheritance, |
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multiple inheritance, and mixin inheritance. In the first part of this paper, |
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we identify and illustrate the conceptual and practical reusability problems |
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that arise with these forms of inheritance. We then present a simple |
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compositional model for structuring object-oriented programs, which we call traits. |
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Traits are essentially groups of methods... (Update) |
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|
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|
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=head3 Hybrid - A Language for Programming with Active Objects |
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|
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http://citeseer.nj.nec.com/561934.html |
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http://citeseer.nj.nec.com/nierstrasz92tour.html |
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http://www.iam.unibe.ch/~scg/Archive/NFS/cao.html |
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|
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=head3 Active Objects and Oberon |
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|
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|
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=head2 DETAILS |
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|
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This attempts to be a runtime wrapper around mixin.pm, written by Michael G Schwern |
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and available on CPAN. |
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Please visit: |
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http://magnonel.guild.net/~schwern/talks/Design_Patterns/full_slides/slide036.html |
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|
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|
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=head2 NOTES |
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|
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## ======== object inheritance ======== |
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|
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2002-12: |
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TODO / REFACTORING PROPOSAL |
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leading from Data::Storage to code abstracted out into this module - DesignPattern::Bridge |
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- this is no inheritance and it doesn't have to be |
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- implement this module as a bridge to its sub-modules |
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- use the BridgePattern (http://c2.com/cgi/wiki?BridgePattern) |
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Using patterns was already successfully done with Data::Storage::Handler |
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by implementing the AdapterPattern (http://c2.com/cgi/wiki?AdapterPattern) |
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with Perl's AUTOLOAD-mechanism |
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- try to use Perl's "tie" command to implement this functionality here instead of using AUTOLOAD! |
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- sub getChildNodes |
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- sub run |
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|
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2003-02-11, joko: Does this have anything in parallel with CPAN's Class::Inner? No! |
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|
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|
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=head1 TODO |
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|
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o use Class::Loader |
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o rename to mixin::runtime? |
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|
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|
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=cut |
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|
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|
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# get logger instance |
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my $logger = eval { Log::Dispatch::Config->instance; }; |
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|
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my $meta; |
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|
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|
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sub DEBUG { 1 } |
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|
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|
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## ======== object constructor ======== |
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sub new { |
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my $invocant = shift; |
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my $class = ref($invocant) || $invocant; |
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my @args = (); |
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@_ && (@args = @_); |
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$logger->debug( __PACKAGE__ . "->new(@args)" ) if $logger; |
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my $self = { @_ }; |
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|
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# trace |
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#print "class: $class", "\n"; |
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|
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# create instance |
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bless $self, $class; |
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|
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# NEW: 2003-04-16 |
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$self->constructor() if $self->can('constructor'); |
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|
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return $self; |
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} |
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|
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|
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## ======== method overrider ======== |
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sub AUTOLOAD2 { |
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|
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my $self = shift; |
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our $AUTOLOAD; |
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|
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##print "AUTOLOAD\n"; |
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|
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my $method = $AUTOLOAD; |
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$method =~ s/^.*:://; |
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|
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$logger->debug( __PACKAGE__ . "->" . $method . "(@_)" . " (AUTOLOAD called, not dispatched)" ) if $logger; |
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|
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## ->DESTROY would - if not declared - trigger an AUTOLOAD also |
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return if $method =~ m/::DESTROY$/; |
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|
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## if ($self->_filter_AUTOLOAD($method)) { |
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## $self->_accessStorage(); |
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## $self->{STORAGEHANDLE}->$method(@_); |
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## } |
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|
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} |
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|
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sub _getPluginPackage { |
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my $self = shift; |
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my $modulename_load = shift; |
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|
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# substitute slashes through double double-colons to load modules perl-style |
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$modulename_load =~ s/\//::/g; |
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|
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# build full package name |
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my $self_classname = ref $self; |
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# name |
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my $package = $modulename_load; |
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|
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# if package is absolute, cut away prefix ('/' or '::') |
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if ($package !~ s/^:://) { |
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# else: prefix with base classname if above name is relative (lacks of '/' or '::') |
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$package = $self_classname . '::' . $package |
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} |
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|
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return $package; |
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} |
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|
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sub load { |
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|
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my $self = shift; |
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my $modulename = shift; |
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my $options = shift; |
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|
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if (ref $modulename eq 'ARRAY') { |
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foreach (@$modulename) { |
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$self->load_single($_, $options); |
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} |
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} else { |
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$self->load_single($modulename, $options); |
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} |
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|
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} |
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|
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sub load_single { |
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|
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my $self = shift; |
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my $modulename_load = shift; |
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|
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my $options = shift; |
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|
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my $self_modulename = ref $self; |
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my $package = $self->_getPluginPackage($modulename_load); |
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|
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if ($meta->{loaded}->{$package}) { |
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return 1; |
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} |
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|
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#$logger->info( __PACKAGE__ . "->load: $package" ) if $logger; |
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#$logger->info( __PACKAGE__ . "->load: $self_modulename" ) if $logger; |
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$logger->debug( $self_modulename . "->load: $package\t[via " . __PACKAGE__ . "]" ) if $logger; |
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|
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# this is the module testing phase - use mixin doesn't seem to propagate errors by default |
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eval("use $package;"); |
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$self->checkExceptions(); |
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|
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=pod |
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if ($@) { |
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$meta->{loaded}->{$package} = 0; |
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# include caller information |
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my @caller = caller; |
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my $caller_msg = $caller[1] . ':' . $caller[2]; |
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my $msg = __PACKAGE__ . "->load: $@ ($caller_msg)"; |
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if ($logger) { |
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$logger->error($msg); |
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} else { |
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print $msg, "\n"; |
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} |
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} |
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=cut |
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|
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#print "ref-1: ", ref $self, "\n"; |
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#print "ref-2: ", ref $self::SUPER, "\n"; |
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|
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# V1: |
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#bless $self, $package; |
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|
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# V2: |
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$self->mixinPackage($package); |
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|
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if (my $method = $options->{method}) { |
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$self->$method(); |
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} |
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|
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return 1; |
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|
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} |
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|
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sub mixinPackage { |
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my $self = shift; |
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my $package = shift; |
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|
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# switch into foreign package and prepare for mixin |
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$self->mixin_prepare($package); |
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|
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# switch into local package (scope which uses DesignPattern::Bridge) and mixin plugin-module |
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$self->mixin_do($package); |
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|
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} |
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|
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# TODO: maybe refactor to DesignPattern::Object? what about the '$logger'? |
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sub mixin_prepare { |
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my $self = shift; |
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my $package = shift; |
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my $self_classname = ref $self; |
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eval("package $package; use mixin::with '$self_classname';"); |
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|
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# FIXME: --- this is redundant --- |
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if ($@) { |
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$meta->{loaded}->{$package} = 0; |
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my $msg = __PACKAGE__ . "->load: $@"; |
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print STDERR $msg, "\n" if DEBUG; |
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$logger->error( $msg ) if $logger; |
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} else { |
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$meta->{loaded}->{$package} = 1; |
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} |
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# FIXME: --- this is redundant --- |
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|
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} |
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|
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sub mixin_do { |
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my $self = shift; |
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my $package = shift; |
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# switch into foreign package and mixin plugin-module |
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my $self_classname = ref $self; |
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eval("package $self_classname; use mixin '$package';"); |
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#eval("use mixin_all '$package';"); |
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|
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# FIXME: --- this is redundant --- |
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if ($@) { |
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$meta->{loaded}->{$package} = 0; |
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$logger->error( __PACKAGE__ . "->load: $@" ) if $logger; |
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} else { |
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$meta->{loaded}->{$package} = 1; |
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} |
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# FIXME: --- this is redundant --- |
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|
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} |
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|
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sub unload { |
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|
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my $self = shift; |
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my $modulename_unload = shift; |
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|
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my $package = $self->_getPluginPackage($modulename_unload); |
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|
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if ($meta->{loaded}->{$package}) { |
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$meta->{loaded}->{$package} = 0; |
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my $where = __PACKAGE__ . ':' . __LINE__; |
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$logger->debug( __PACKAGE__ . "->unload: FIXME: DESTROY object is not implemented at '$where'." ) if $logger; |
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} |
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|
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} |
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|
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|
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sub boot { |
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my $self = shift; |
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$self->_abstract_function('boot'); |
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} |
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|
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sub include { |
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my $self = shift; |
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my $includefile = shift; |
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my $package = shift; |
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|
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# pre-flight checks |
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if (!$includefile) { |
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$self->raiseException('Filename for inclusion was empty.'); |
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return; |
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} |
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|
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# go for it ... |
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eval("require '$includefile';"); |
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# ... and handle errors afterwards catching every message from perl itself ... |
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return if $self->checkExceptions(); |
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|
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# ... otherwise continue assuming everything is fine |
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$self->mixinPackage($package) if $package; |
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|
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} |
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|
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1; |
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__END__ |
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