Abstract factory

El patró de disseny Abstract factory permet crear diferents famílies d'objectes.

Estructura

El diagrama de classes és el següent:

En Lepus3 (llegenda):

Codis d'exemple

Java

/* GUIFactory example -- */
 
interface GUIFactory {
 public Button createButton();
}
 
 
class WinFactory implements GUIFactory {
 public Button createButton() {
 return new WinButton();
 }
}
 
 
class OSXFactory implements GUIFactory {
 public Button createButton() {
 return new OSXButton();
 }
}
 
 
 
interface Button {
 public void paint();
}
 
 
class WinButton implements Button {
 public void paint() {
 System.out.println("I'm a WinButton");
 }
}
 
 
class OSXButton implements Button {
 public void paint() {
 System.out.println("I'm an OSXButton");
 }
}
 
 
class Application {
 public Application(GUIFactory factory){
 Button button = factory.createButton();
 button.paint();
 }
}
 
public class ApplicationRunner {
 public static void main(String[] args) {
 new Application(createOsSpecificFactory());
 }
 
 public static GUIFactory createOsSpecificFactory() {
 int sys = readFromConfigFile("OS_TYPE");
 if (sys == 0) {
 return new WinFactory();
 } else {
 return new OSXFactory();
 }
 }
}

La sortida del programa hauria de ser "I'm a WinButton" o "I'm a OSXButton" depenent del tipus de factoria usat. Tingueu en compte que l'aplicació no té ni idea de quin tipus de GUIFactory es dóna, o fins i tot quin tipus de botó que genera la fàbrica.

C++

/* a GUIFactory exemple en C++ */
 
struct GUIFactory{
 virtual Button* createButton () = 0;
};
 
struct WinGUIFactory : public GUIFactory{
 Button* createButton (){
 return new WinButton();
 }
};
 
struct OSXGUIFactory : public GUIFactory{
 Button* createButton (){
 return new OSXButton();
 }
};
 
struct Button{
 virtual void paint() = 0;
};
 
struct WinButton : public Button{
 void paint (){
 std::cout << " I'm a window button \n";
 }
};
 
struct OSXButton : public Button{
 void paint (){
 std::cout << " I'm a OSX button \n";
 }
};
 
struct Application {
 Application(GUIFactory* factory){
 Button * button = factory->createButton();
 button->paint();
 }
};
 
/* application code */
 
int main()
{
 GUIFactory* factory1 = new WinFactory();
 GUIFactory* factory2 = new OSXFactory();
 
 Application* winApp = new Application (factory1); 
 Application* osxApp = new Application (factory2);
 
 delete factory1, factory2;
 
 return 0;
}

---

Enllaços externs

• Abstract Factory (anglès)
• Abstract Factory (anglès)
• Abstract Factory on the Net Objectives Repository (anglès)
• Jt J2EE Pattern Oriented Framework (anglès)
• C++ Abstract Factory C++ abstract factory design and tutorial (anglès)