Re: howto dispatch to derived classes?

[Ali Çehreli]

On 10/14/2013 02:09 PM, Manfred Nowak wrote:

>> class C{}
>>    class C1:C{}
>>    // ...
>>    class Cn:C{}
>>
>> C getC(){ return new Cn;} // might be extern
>>                            // and deliver some Ci
>>
>> void visit( C1 fp){}
>> // ...
>> void visit( Cn fp){}
>> void main(){
>>    visit( getC);           // dispatch?
>> }
>
> -manfred
>
>            visit( getC);
>          }
>
>
That it not exactly the same but looks like the visitor pattern. The 
actual type of the object is implicitly stored in the vtbl of each type. 
So, a virtual function like accept() can do the trick:

import std.stdio;

class C{
    abstract void accept();
}

class C1:C {
    override void accept() { visit(this); }
}

class Cn:C{
    override void accept() { visit(this); }
}

C getC(){ return new Cn;} // might be extern
                          // and deliver some Ci

void visit( C1 fp) {
    writeln("visiting C1");
}

void visit( Cn fp){
    writeln("visiting Cn");
}
void main(){
    getC().accept();
}

Ali