Classes (does this make sense?)

[Ary Borenszweig]

Saaa escribió:
> Let me ask some more specific questions ..
> 
> in the previous thread people suggested using the following:
> 
> static this()
> {
>      APPLE = new class() IFruit {
>          void eat() {
>              writefln("Eat APPLE");
>          }
>      };
> 
>      PEAR = new class() IFruit {
>          void eat() {
>              writefln("Eat PEAR");
>          }
>      };
> }
> 
> Why the 'new class()' ? Couldn't you just create a class apple : IFruit ?
> Those fruits are in reality quite big, with multiple functions/local 
> variables.

Yes. In fact, I would recommend to do that and not use the anonymous 
approach, specially if the classes are big. They probably showed it like 
that for brevity purposes.

> I've tried placing the APPLE in another module:
> -----------------------------
> module apple;
> 
> import std.stdio;
> import main;
> 
> class APPLE : IFruit {
>    void eat() {
>       writefln("Eat APPLE");
>    }
> }
> ------------------------------
> module main;
> 
> import std.stdio;
> import apple;
> 
> interface IFruit
> {
>      void eat();
> }
> 
> IFruit APPLE;

Here you declare a variable of type IFruit called APPLE.

> IFruit PEAR;
> IFruit PLUM;
> 
> static this()
> {
>      PEAR = new class() IFruit {
>          void eat() {
>              writefln("Eat PEAR");
>          }
>      };
> 
>      PLUM = new class() IFruit {
>          void eat() {
>              writefln("Eat PLUM");
>          }
>      };

But you never initialize it, so it's null. That's why you get access 
violation error.

> }
> 
> int main(string[] args) {
> 
> IFruit[] fruits = [APPLE, PEAR, APPLE, APPLE, PEAR, PLUM];
> 
> writefln("Fruits");
> foreach( f; fruits) {
> f.eat();
> }
> 
> return 0;
> }
> ---------------------------------
> 
> Fruits
> Error: Access Violation
> 
> :) 
> 
>