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Prototype

19,532 bytes added, 22:21, 29 March 2007

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== Advantages ==

<ul>

<li>Enables definition of new objects with various structure</li>

<li>Facilitates Adding and removing new types of objects at run time</li>

<li>Hides the Concrete class structure from clients</li>

<li>Reduces the amount of subclasses</li>

</ul>

~~== Side Effects ==~~

== Pattern diagram ==

<Center>[[Image:prototype.jpg]]</center>

== Sample code ==

'''Java Sample:'''

Prototype pattern in java is implemented using the Clonable interface which provides the clone() method. Cloneable is an empty interface. It simply acts as a tag to indicate that the implementing classes need their instances to support clonning.

Subclasses must implement the Clonable interface and then override the clone() method and call the super classes clone method in the implementation of overridden clone method using super.clone() statement.If you don't implement Cloneable, the super.clone() implementation will throw a CloneNotSupportedException.

~~Subclasses must implement~~ The following is the implementation of Cookie class in apache tomcat server. This class makes use of prototype pattern and Clonable interface ~~and then override the clone() method and call the super classes clone method in the implementation~~ to create clones of ~~overridden clone method using super.clone() statement~~cookie object.~~If you don't implement Cloneable, the super~~[http://en.~~clone() implementation will throw a CloneNotSupportedException~~wikipedia. org/wiki/Apache_HTTP_Server Apache]

~~The following is the implementation of Cookie class in apache tomcat server. This class makes use of prototype pattern and Clonable interface to create clones of cookie object.~~

apache-tomcat-6.0.10 - Cookie.java

<pre>

/*

// so long as sun.servlet.* must run on older JDK 1.02 JVMs which

// don't include that support.

*****************************************************************************************************************************

** Implementing the Clonable Interface **

*****************************************************************************************************************************

public class Cookie implements Cloneable {

*

*/

************************************************************************************************************************************************************************************************************************************************************ Overriding the Clone Method and calling the super class Clone method ************************************************************************************************************************************************************************************************************************************************************

public Object clone() {

try {

}

</pre>

----

'''C++ Sample:'''

The following classe is a sample of prototype pattern implementation used in GNU Image Manipulation Program(gimp-2.3.15). The prototypical class is ''imap_object.c'' that defines the ''object_clone'' method.[http://en.wikipedia.org/wiki/GIMP GIMP]

imap_object.h

<pre>

/*

* This is a plug-in for the GIMP.

*

* Generates clickable image maps.

*

* This program is free software; you can redistribute it and/or modify

* it under the terms of the GNU General Public License as published by

* the Free Software Foundation; either version 2 of the License, or

* (at your option) any later version.

*

* This program is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

* GNU General Public License for more details.

*

* You should have received a copy of the GNU General Public License

* along with this program; if not, write to the Free Software

* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

*

*/

#ifndef _IMAP_OBJECT_H

#define _IMAP_OBJECT_H

typedef struct Object_t Object_t;

typedef struct ObjectClass_t ObjectClass_t;

typedef struct ObjectList_t ObjectList_t;

#include "imap_edit_area_info.h"

#include "imap_menu_funcs.h"

*****************************************************************************************************************************

** Object_t Sturcture Definition on the header file **

*****************************************************************************************************************************

struct Object_t {

ObjectClass_t *class;

ObjectList_t *list;

gint refcount;

gboolean selected;

gboolean locked;

gchar *url;

gchar *target;

gchar *comment;

gchar *mouse_over;

gchar *mouse_out;

gchar *focus;

gchar *blur;

};

typedef void (*MoveSashFunc_t)(Object_t*, gint, gint);

typedef void (*OutputFunc_t)(gpointer, const char*, ...);

struct AreaInfoDialog_t;

struct ObjectClass_t {

...

};

Object_t *object_ref(Object_t *obj);

void object_unref(Object_t *obj);

Object_t* object_init(Object_t *obj, ObjectClass_t *class);

Object_t* object_clone(Object_t *obj);

Object_t* object_assign(Object_t *src, Object_t *des);

void object_draw(Object_t *obj, GdkWindow *window);

void object_edit(Object_t *obj, gboolean add);

void object_select(Object_t *obj);

void object_unselect(Object_t *obj);

void object_move(Object_t *obj, gint dx, gint dy);

void object_remove(Object_t *obj);

void object_lock(Object_t *obj);

void object_unlock(Object_t *obj);

void object_set_url(Object_t *obj, const gchar *url);

void object_set_target(Object_t *obj, const gchar *target);

void object_set_comment(Object_t *obj, const gchar *comment);

void object_set_mouse_over(Object_t *obj, const gchar *mouse_over);

void object_set_mouse_out(Object_t *obj, const gchar *mouse_out);

void object_set_focus(Object_t *obj, const gchar *focus);

void object_set_blur(Object_t *obj, const gchar *blur);

gint object_get_position_in_list(Object_t *obj);

void object_emit_changed_signal(Object_t *obj);

void object_emit_geometry_signal(Object_t *obj);

void object_emit_update_signal(Object_t *obj);

#define object_is_valid(obj) \

((obj)->class->is_valid(obj))

#define object_get_dimensions(obj, x, y, width, height) \

((obj)->class->get_dimensions((obj), (x), (y), (width), (height)))

#define object_normalize(obj) \

((obj)->class->normalize(obj))

#define object_resize(obj, per_x, per_y) \

((obj)->class->resize((obj), (per_x), (per_y)))

#define object_update(obj, data) \

((obj)->class->update((obj), (data)))

#define object_update_info_widget(obj, data) \

((obj)->class->update_info_widget((obj), (data)))

#define object_fill_info_tab(obj, data) \

((obj)->class->fill_info_tab((obj), (data)))

#define object_get_stock_icon_name(obj) \

((obj)->class->get_stock_icon_name())

typedef struct {

Object_t *obj;

gboolean (*finish)(Object_t *obj, gint x, gint y);

gboolean (*cancel)(GdkEventButton *event, Object_t *obj);

Object_t* (*create_object)(gint x, gint y);

void (*set_xy)(Object_t *obj, guint state, gint x, gint y);

} ObjectFactory_t;

gboolean object_on_button_press(GtkWidget *widget, GdkEventButton *event,

gpointer data);

typedef struct {

GList *list;

} ObjectListCallback_t;

struct ObjectList_t {

...

};

ObjectList_t *make_object_list (void);

void object_list_destruct(ObjectList_t *list);

ObjectList_t *object_list_copy(ObjectList_t *des, ObjectList_t *src);

ObjectList_t *object_list_append_list(ObjectList_t *des, ObjectList_t *src);

void object_list_append(ObjectList_t *list, Object_t *object);

void object_list_prepend(ObjectList_t *list, Object_t *object);

void object_list_insert(ObjectList_t *list, gint position, Object_t *object);

void object_list_remove(ObjectList_t *list, Object_t *object);

void object_list_remove_link(ObjectList_t *list, GList *link);

void object_list_update(ObjectList_t *list, Object_t *object);

void object_list_draw(ObjectList_t *list, GdkWindow *window);

void object_list_draw_selected(ObjectList_t *list, GdkWindow *window);

Object_t *object_list_find(ObjectList_t *list, gint x, gint y);

Object_t *object_list_near_sash(ObjectList_t *list, gint x, gint y,

MoveSashFunc_t *sash_func);

gint object_list_cut(ObjectList_t *list);

void object_list_copy_to_paste_buffer(ObjectList_t *list);

void object_list_paste(ObjectList_t *list);

void object_list_remove_all(ObjectList_t *list);

void object_list_delete_selected(ObjectList_t *list);

void object_list_edit_selected(ObjectList_t *list);

gint object_list_select_all(ObjectList_t *list);

void object_list_select_next(ObjectList_t *list);

void object_list_select_prev(ObjectList_t *list);

gint object_list_select_region(ObjectList_t *list, gint x, gint y, gint width,

gint height);

gint object_list_deselect_all(ObjectList_t *list, Object_t *exception);

gint object_list_nr_selected(ObjectList_t *list);

void object_list_resize(ObjectList_t *list, gint percentage_x,

gint percentage_y);

void object_list_move_selected(ObjectList_t *list, gint dx, gint dy);

void object_list_move_up(ObjectList_t *list, Object_t *obj);

void object_list_move_down(ObjectList_t *list, Object_t *obj);

void object_list_move_selected_up(ObjectList_t *list);

void object_list_move_selected_down(ObjectList_t *list);

void object_list_move_to_front(ObjectList_t *list);

void object_list_send_to_back(ObjectList_t *list);

void object_list_write_csim(ObjectList_t *list, gpointer param,

OutputFunc_t output);

void object_list_write_cern(ObjectList_t *list, gpointer param,

OutputFunc_t output);

void object_list_write_ncsa(ObjectList_t *list, gpointer param,

OutputFunc_t output);

typedef void (*ObjectListCallbackFunc_t)(Object_t*, gpointer);

gpointer object_list_add_changed_cb(ObjectList_t *list,