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?

KeepYourMind wrote:
> 
> What i need to do for pizza.doSomeA() begin work?

cast pizza to CoolPizza.

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.

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( );
   }
}

> 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

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();
}

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. :-(

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.