AW: [Xotcl] destroy invoked by object move?

[Kristoffer Lawson]

On 17 Mar 2006, at 16:33, Gustaf Neumann wrote:
>
> as pointed out earlier, move is a copy + destroy.
> If you want a copy alone, use copy and not move.

No, I do not want copy alone. It is just counter-intuitive that the  
destructor is called on a move as movement is not generally  
considered to be an act of desctruction. This would be the norm for  
most things. Consider files for example. When a file is moved at no  
point does

> As Artur pointed out, command names are the references to objects.
> if such a reference should be made invalid and the unneeded
> storage should be reclaimed at this time, destroy is the correct  
> thing.

The matter of references is problematic. I am thinking that in fact  
this reveals a downside to the namespace-tied model as handles do not  
point to the object itself, but to the object's location within the  
namespace universe. A move is not actually a matter of transferring  
the ownership of an object to a new location and this slightly limits  
the ways you can use XOTcl move functionality for data structures.

Of course one can set variables to detect this, as mentioned, but  
this seems like a bit of a hack and fighting against what XOTcl is  
doing. Perhaps the question should be asked: how is object movement  
actually supposed to be used in XOTcl?

A double-reference would solve this. In that way the handle returned  
by [new]  and [self] would always be a valid command for the object,  
throughout its whole lifetime. If it is moved to be a child of  
another object the handle remains the same (or at least can be used),  
but the ownership is changed. Whether this is workable in XOTcl or  
not is, of course, something you would be better at deciding.

In any case, the destruction should be clearly mentioned in the  
documentation as there seems to be a number of people who are  
surprised by that.

            /  http://www.fishpool.com/~setok/