null [re: spec#]

[Simen kjaeraas]

Nick Sabalausky <a at a.a> wrote:
> If you do that, then there's two possibilities:
>
> A. You intended p to get inited on all code paths but forgot a codepath.
> With real init-checking the compiler will tell you and you can fix it.  
> With
> D as it is, you're not informed at all, and you may or may not catch the
> problem before deployment. Obviously the former is better.
>
> B. You *intended* p to not always be inited, in which case the correct  
> code
> is this:
>
> void foo( ) {
>   Object p=null;
>   if ( m ) {
>     p = new Object( );
>     p.DoSomethingThatNeedsToBeDoneNow( );
>   }
>   // 20 lines of code here
>   if ( p != null ) {
>     p.doSomethingWeird( dataFromAbove );
>   }
> }

There is a third option, wherein the if condition will only be true if
p !is null, but the actual condition is more complex:

if ( m > 4 ) {
     p = new Object( );
     p.DoSomethingThatNeedsToBeDoneNow( );
}

// code

if ( m > 12 ) {
     p.doSomethingWeird( dataFromAbove );
}


-- 
Simen