I dont understand casting well. I see the following line in a program

obj[0] = cast(Object) new ArrayWrapperString(data);

Does ArrayWrapperString() exist in the Tango library  (I did not find it) or does this automatically create an instance of new type and create the type too. ?
Where could I read up on this ?

"Tower Ty" <tytower@yahoo.com.au> wrote in message news:fsp4ft$7no$1@digitalmars.com...
>I dont understand casting well. I see the following line in a program
>
> obj[0] = cast(Object) new ArrayWrapperString(data);
>
> Does ArrayWrapperString() exist in the Tango library  (I did not find it)
> or does this automatically create an instance of new type and create the
> type too. ?
> Where could I read up on this ?
>

The syntax "new Class(args)" constructs a new instance of a class on the heap. This will allocate memory for the instance and call the constructor that takes the arguments that are supplied in the parenthises.

The syntax "cast(type)" is a unary prefix operator that takes one argument (in this case the newly constructed ArrayWrapperString instance) and explicitly casts in to a reference of type Type (in this case Object).

Given that all classes in D inherit implicitly from class Object and I believe you should be able to implicitly cast an instance to a reference to any ancestor class I'd be surprised if the explicit cast was necessary.

The ArrayWrapperString class must be defined, no automatic type-creation occurs, and given this is from a DWT example I can only assume that it is declared as part of that library, though as it uses Tango it could also be in there - I'm personally familiar with neither.

If it was me I'd:

    grep -R "ArrayWrapperString" *

wherever I'd put my Tango/DWT source files to look for the declaration given that some quick google/digitalmars searching proved relatively fruitless.

Hope that puts you on the right track.

Thanks Neil
I found it as a alias added later
module dwt.dwthelper.utils;