Adding the ?. null verification

[H. S. Teoh via Digitalmars-d]

On Thu, Jun 19, 2014 at 04:29:12PM -0400, Etienne via Digitalmars-d wrote:
> On 2014-06-19 3:11 PM, H. S. Teoh via Digitalmars-d wrote:
> >
> >	safeDeref(obj).subobj.prop.field.failsafe!val(defaultVal)
> >
> >where the last element is passed as an alias to the failsafe template,
> >which then does the .init-replacement magic. It looks a lot uglier,
> >though. :-(
> >
> >
> >T
> >
> 
> meh, this works:
> 
> 
> writeln(currAssignment.safeDeref.typeInfo.ident.or("meh"));
> 
> ..
> 	static struct SafeDeref {
> 		T t;
> 		
> 		// Make the wrapper as transparent as possible.
> 		alias t this;
> 
> 		// this overrides if null
> 		T or(T defVal){
> 			if (t is t.init)

This assumes that t.init is not a possible valid field value. But in
that case, there's no need to remap it, you just check for t.init
instead. For pointers, where .init is null, this isn't a problem, but
for things like int, where 0 is possible valid value, you may be
accidentally mapping 0 to the default value when the given field
actually exists (and has value 0)!


> 			{
> 				return defVal;
> 			}
> 			else
> 			{
> 				return t;
> 			}
> 			
> 		}
> ..


T

-- 
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