Hi,

I have a simple struct and i want to check if a variable has been asigned:

struct hello
{

}
...
hello h;
...
if(!h)
{
do stuff;
}

When compiling i get erros about opCall not implemented and many others. What can i do?

Thanks in advance.

Heinz wrote:
> Hi,
> 
> I have a simple struct and i want to check if a variable has been asigned:
> 
> struct hello
> {
> 
> }
> ...
> hello h;
> ...
> if(!h)
> {
> do stuff;
> }
> 
> When compiling i get erros about opCall not implemented and many others. What can i do?
> 
> Thanks in advance.

Structs are value types. Read the spec. Then use a pointer :)

hello* h;

if (!h) h = new hello;

 --downs

downs Wrote:

> Heinz wrote:
> > Hi,
> > 
> > I have a simple struct and i want to check if a variable has been asigned:
> > 
> > struct hello
> > {
> > 
> > }
> > ...
> > hello h;
> > ...
> > if(!h)
> > {
> > do stuff;
> > }
> > 
> > When compiling i get erros about opCall not implemented and many others. What can i do?
> > 
> > Thanks in advance.
> 
> Structs are value types. Read the spec. Then use a pointer :)
> 
> hello* h;
> 
> if (!h) h = new hello;
> 
>  --downs

Thanks for your reply. Can i use then?:
 hello h;
if(!&h)

On Tue, 29 Apr 2008 06:50:18 +0200, Heinz <malagana15@yahoo.es> wrote:

> downs Wrote:
>> Structs are value types. Read the spec. Then use a pointer :)
>>
>> hello* h;
>>
>> if (!h) h = new hello;
>>
>>  --downs
>
> Thanks for your reply. Can i use then?:
>  hello h;
> if(!&h)


No. &h will always return a non-null pointer (h exists, in other words).

You might use some convoluted workaround to make hello aware of whether or
not it has been assigned something.

Easy example:

struct hello
{
  bool assigned;
  // other fields;
}

hello h;

h = hello(true, ...);

if (h.assigned)
  DoSomethingOrOther();


This may or may not be enough for you needs.

-- Simen

Heinz wrote:
> downs Wrote:
> 
>> Heinz wrote:
>>> Hi,
>>>
>>> I have a simple struct and i want to check if a variable has been asigned:
>>>
>>> struct hello
>>> {
>>>
>>> }
>>> ...
>>> hello h;
>>> ...
>>> if(!h)
>>> {
>>> do stuff;
>>> }
>>>
>>> When compiling i get erros about opCall not implemented and many others. What can i do?
>>>
>>> Thanks in advance.
>> Structs are value types. Read the spec. Then use a pointer :)
>>
>> hello* h;
>>
>> if (!h) h = new hello;
>>
>>  --downs
> 
> Thanks for your reply. Can i use then?:
>  hello h;
> if(!&h)

No.
Structs are *value types*.

That means, unless _explicitly newed_ (or part of a struct that's explicitly newed), they _always_ live on the stack.

Ergo, if &h is null, your complete callstack is shot :)

 --downs