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digitalmars.D.learn - Factory class

reply KeepYourMind <vyacheslav blue-code.org> writes:
Hello. I'm try to write factory class but have some problems.
Source example:

// Pizza interface
interface IPizza
{
    void doSome();
}

// Pizza
class IMPizza : IPizza
{
    void doSome() {}
}

// try to raise functinally
class CoolPizza : IPizza
{
    void doSome() {}
    void doSomeA() {}
}

// Factory
static class PizzaFactory
{
    static IPizza factory(char[] name)
    {
        switch (name) {
            case "im":
                return new IMPizza;
                break;
            case "cool":
                return new CoolPizza;
                break;
            default:
                throw new Exception("incorrect pizza name");
                break;
        }
    }
}

// run
void main()
{
    auto pizza = PizzaFactory.factory();
    pizza.doSome(); // OK
    pizza.doSomeA(); // error: IPizza.doSomeA() not found
}

What i need to do for pizza.doSomeA() begin work?
Mar 19 2009
next sibling parent reply Sean Kelly <sean invisibleduck.org> writes:
KeepYourMind wrote:

 
 What i need to do for pizza.doSomeA() begin work?


cast pizza to CoolPizza.
Mar 19 2009
parent reply KeepYourMind <vyacheslav blue-code.org> writes:
Sean Kelly Wrote:


 KeepYourMind wrote:

 
 What i need to do for pizza.doSomeA() begin work?


 
 cast pizza to CoolPizza.


Problem is i dont know what class returned. "char[] name" is dynamic and
getting from command-line arguments.
Mar 19 2009
parent reply "Simen Kjaeraas" <simen.kjaras gmail.com> writes:
On Thu, 19 Mar 2009 18:06:37 +0100, KeepYourMind <vyacheslav blue-code.org>
wrote:


 Sean Kelly Wrote:


 KeepYourMind wrote:

 What i need to do for pizza.doSomeA() begin work?


 cast pizza to CoolPizza.


 Problem is i dont know what class returned. "char[] name" is dynamic and  
 getting from command-line arguments.


Then you need some test to see if it really is a CoolPizza.

void main( string[] args ) {
    auto pizza = PizzaFactory.factory( args[1] );
    pizza.doSome( );
    if ( args[1] == "CoolPizza" ) {
        ( cast( CoolPizza ) pizza ).doSomeA( );
    }
}
Mar 19 2009
parent reply "Denis Koroskin" <2korden gmail.com> writes:
On Thu, 19 Mar 2009 22:58:02 +0300, Simen Kjaeraas <simen.kjaras gmail.com>
wrote:


 On Thu, 19 Mar 2009 18:06:37 +0100, KeepYourMind  
 <vyacheslav blue-code.org> wrote:


 Sean Kelly Wrote:


 KeepYourMind wrote:

 What i need to do for pizza.doSomeA() begin work?


 cast pizza to CoolPizza.


 Problem is i dont know what class returned. "char[] name" is dynamic  
 and getting from command-line arguments.


 Then you need some test to see if it really is a CoolPizza.

 void main( string[] args ) {
     auto pizza = PizzaFactory.factory( args[1] );
     pizza.doSome( );
     if ( args[1] == "CoolPizza" ) {
         ( cast( CoolPizza ) pizza ).doSomeA( );
     }
 }


Not like that. Here is a better way:

auto pizza = PizzaFactory.factory( name );
pizza.doSome();
if (auto cool = cast(CoolPizza)pizza) {
    cool.doSomeA();
}
Mar 19 2009
parent KeepYourMind <vyacheslav blue-code.org> writes:
Denis Koroskin Wrote:


 On Thu, 19 Mar 2009 22:58:02 +0300, Simen Kjaeraas <simen.kjaras gmail.com>
wrote:
 

 On Thu, 19 Mar 2009 18:06:37 +0100, KeepYourMind  
 <vyacheslav blue-code.org> wrote:


 Sean Kelly Wrote:


 KeepYourMind wrote:

 What i need to do for pizza.doSomeA() begin work?


 cast pizza to CoolPizza.


 Problem is i dont know what class returned. "char[] name" is dynamic  
 and getting from command-line arguments.


 Then you need some test to see if it really is a CoolPizza.

 void main( string[] args ) {
     auto pizza = PizzaFactory.factory( args[1] );
     pizza.doSome( );
     if ( args[1] == "CoolPizza" ) {
         ( cast( CoolPizza ) pizza ).doSomeA( );
     }
 }


 
 Not like that. Here is a better way:
 
 auto pizza = PizzaFactory.factory( name );
 pizza.doSome();
 if (auto cool = cast(CoolPizza)pizza) {
     cool.doSomeA();
 }
 


Got it. If use one from this ways i'm not need factory, only switch. Bad. :-(
Mar 20 2009
prev sibling parent reply dennis luehring <dl.soluz gmx.net> writes:
 void main()
 {
     auto pizza = PizzaFactory.factory();
     pizza.doSome(); // OK
     pizza.doSomeA(); // error: IPizza.doSomeA() not found
 }


you interface has only doSome() and that is what factory returns

and for all others: factories and cast don't belong together

you interface should fit your overall needs
Mar 19 2009
parent KeepYourMind <vyacheslav blue-code.org> writes:
dennis luehring Wrote:


 void main()
 {
     auto pizza = PizzaFactory.factory();
     pizza.doSome(); // OK
     pizza.doSomeA(); // error: IPizza.doSomeA() not found
 }


 
 you interface has only doSome() and that is what factory returns
 
 and for all others: factories and cast don't belong together
 
 you interface should fit your overall needs


Got it. Thanks to all.
Mar 20 2009