digitalmars.D.learn - Cast to a new type
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 ?
Mar 30 2008
"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.
Mar 30 2008
Thanks Neil I found it as a alias added later module dwt.dwthelper.utils;
Mar 30 2008