Suggestion: properties should be treated as 'virtual members variables'

[Chad J]

Just thought I'd point out another shortcoming of the current approach 
to properties.
Suppose you have the following code:

class Foo
{
   void delegate() bar;

   void func()
   {
     writefln( "example" );
   }

   this()
   {
     bar = &func;
   }
}

void main()
{
   Foo foo = new Foo();
   foo.bar();
}

This prints "example".  But now the class is rewritten so that the 
delegate is hidden behind a property:

class Foo
{
   void delegate() m_bar;
   void delegate() bar() { return m_bar; }

   void func()
   {
     writefln( "example" );
   }

   this()
   {
     m_bar = &func;
   }
}

void main()
{
   Foo foo = new Foo();
   foo.bar();
}

Unfortunately this still compiles and runs...  incorrectly.  It prints 
nothing.  foo.bar() just returns a delegate, but doesn't call it.

IMO, this is quite underpowered compared to what something like C# gives 
you.  Currently it's just shorthand for function calling, and that 
hardly helps me.  I don't mind typing a few extra characters to call a 
function.  What I want is to be able to treat properties as data members 
in /every/ way on the calling side.

I hope there are plans to change the current state of properties at some 
point, regardless of backwards compatibility.

Kristian wrote:
> 
> In digitalmars.D.announce there has been discussion about why you 
> cannot  use properties as data members. For example, why the following 
> (simple)  example doesn't work:
> 
> class A {
>     int prop() {return m_val;}
>     int prop(int val) {return m_val = val;}
> 
>     int m_val = 0;
> }
> 
> void f(inout int x) {
>     x++;
> }
> 
> void func() {
>     A a = new A;
> 
>     f(a.prop);  //error: ((a).prop)() is not an lvalue
> }
> 
> 
> I think properties should work just like they were data members:  
> everywhere you could give a data member you can also give a property. 
> So,  for example, the following should also work:
> 
> a.prob++;
> a.prob -= 10;
> 
> Hence the implementation of 'prob' will be hidden from the user.
> 
> I would very much see properies as a 'virtual member variables'.
> 
> 
> Hmm, would it be simplier to implement properties by using virtual 
> tables  for variables?...
> 
> (What object oriented languages did for functions, D does it for  
> variables! *grin*)