hijacking a class's members

[Rory Mcguire]

Mafi wrote:

>> Thats what feels weird to me. a.x can result in different things
>> happening even though x exists in both A and the generated class. However
>> the generated class has two "fields" called x one you can't access
>> anymore and the @property one.
>> When I create an instance of the generated class I would expect it to
>> always to the same thing if I use one of its methods/properties/etc...
>> Kind of like you would expect the following to print out "hello 2":
>> class A {
>>      string toString() { return "hello"; }
>> }
>> class B : A {
>>      string toString() { return super.toString() ~ " 2"; }
>> }
>> void main() {
>>      A a = new B();
>>      writeln(a.toString()); // uses B.toString()
>> }
>>
>> What I've got is:
>> class A {
>>      int x;
>> }
>> class B : A {
>>      int x() { throw new Exception(); }
>> }
>> void main() {
>>      A a = new B();
>>      writeln(a.x); // this accesses A.x not B.x!!!!
>> }
>>
>> just seems like properties are not quite right or something.
>>
>> -Rory
>>
> 
> If you want that to work, both x have to be virtual (ie dynamically
> bound). In D all non-final non-ststic clsss-methods are virtual(1).
> Consider the following:
> ///////
> class A {
>    int x = 0;
>    int getX() { //<-- it's virtual
>      return x;
>    }
> }
> 
> class B : A{
>    int x = 5;
>    override int getX() { //<-- it's virtual too
>      return x;
>    }
> }
> 
> void thinAboutA(A a) {
>    /* Now a call to a non virtual method
>     * which results in vtbl lookup. a's vtbl
>     * contains B.getX().
>    writeln(a.getX());
>    /* Non virtual field.
>     * Has to be statically bound
>     * to a lookup in A.x
>     */
>    writeln(a.x);
> }
> 
> void main() {
>    thinkAboutA(new B);
> }
> ////////
> 
> Fields have to be statically bound bcause the compiler doesn't enforce
> covariance with fields. So you can:
> ///////////////
> class C : A {
>    string x = "";
> }
> 
> void main()  {
>    thinkAboutA(new C); //Should evrything crash now? I won't.
> }
> //////////////
> 
> 1) I'm not sure about @propertys.


cool thanks

good example