Am 18.08.2016 15:09 schrieb "Felipe Monteiro de Carvalho" < felipemonteiro.carva...@gmail.com>: > > On Thu, Aug 18, 2016 at 2:44 PM, Sven Barth <pascaldra...@googlemail.com> wrote: > > generic procedure WriteVector_To_DM<T>(ADest: TDataManager; ASelf: > > specialize TVector<T>); > > generic procedure ReadVector_From_DM<T>(AFrom: TDataManager; var ASelf: > > specialize TVector<T>); > > > > and use them like this: > > > > specialize WriteVector_To_DM<TSubClass1>(...); > > Aha, great, didn't know we had something in this direction. But > correct me if I am wrong, but this wouldn't work in my case, because > my function writes the class to a stream in the end of it, so it needs > to know which type T is. If the type is TSomeClass or a descendent, > then it will write each field of the class to the stream. > > But in a generic class/function there is no way to ask if T is an int, > or is an TSomeClass, or am I missing some way of writing code that is > different for various possible types?
You can enforce that T needs to be a subclass of TSomeClass by declaring it as "T: TSomeClass"; like this: generic procedure WriteVector_To_DM<T: TSomeClass>(ADest: TDataManager; ASelf: specialize TVector<T>); In that case the compiler knows that T will at least be a TSomeClass so you can use methods and fields of it without problems. Note: these generic constraints also work for generic types and is already in 3.0.0 for them. Additionally you can play around with TypeInfo() which works on variables of a generic type as well. Regards, Sven
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