hi,

i like to copy objects such as:

class A {....}

A xxx; // some things are done ...

A yyy = xxx;

how can one do that in D2 easy? are any samples?

thanks

Reply to lurker,

> hi,
> 
> i like to copy objects such as:
> 
> class A {....}
> 
> A xxx; // some things are done ...
> 
> A yyy = xxx;
> 
> how can one do that in D2 easy? are any samples?
> 
> thanks
> 

first, classes are reference types so the above needs to be:

A xxx = new A;
// some things are done ...
A yyy = xxx;

second, that assignment will work as is but will act as a reference copy (you get two copies of the reference to the same object). If you want a real copy you can use structs or generate a deep copy function for the class. I don't use 2.0 so someone else will need to fill in the details.

On Mon, 02 Jun 2008 20:08:29 +0400, lurker <lurker@lurker.com> wrote:

> hi,
>
> i like to copy objects such as:
>
> class A {....}
>
> A xxx; // some things are done ...
>
> A yyy = xxx;
>
> how can one do that in D2 easy? are any samples?
>
> thanks
>
>

You shouldn't use this for by design, it's not supported for reference types, only for structs.
But you might consider wrapping the class into a struct with overloaded opAssign semantics.
It sould work fine for you (after opImplicitCast is implemented :)).

The other limitation of opAssign is that you can't override opAssign to accept object of the same type:

T t1;
T t2;
t1 = t2; // can't be hooked :(

Compiler just makes a plain bitwise copy of the object in any case.

I was trying to implement C++-style reference (Ref!(T) template), it works fine but the I didn't find any way to disallow reference rebindment:

int i = 5;
Ref!(int) ri = i;

ri = 0;
assert(ri == i);

--ri;
assert(ri == i);

ri *= 2;
assert(ri == i);

ri ^= 4;
assert(ri == i);

int t = 0;

ri = Ref!(int)(&t);	// that's what I want to disallow, but can't :(
assert(ri == i);

Anyone knows how to workaround this?

Reply to Koroskin,

> On Mon, 02 Jun 2008 20:08:29 +0400, lurker <lurker@lurker.com> wrote:
> 
>> hi,
>> 
>> i like to copy objects such as:
>> 
>> class A {....}
>> 
>> A xxx; // some things are done ...
>> 
>> A yyy = xxx;
>> 
>> how can one do that in D2 easy? are any samples?
>> 
>> thanks
>> 
> You shouldn't use this for by design, it's not supported for reference
> types, only for structs.
> But you might consider wrapping the class into a struct with
> overloaded
> opAssign semantics.
> It sould work fine for you (after opImplicitCast is implemented :)).
> The other limitation of opAssign is that you can't override opAssign
> to  accept object of the same type:
> 

It's not really clean but making a dup() method would be constant with D's arrays.