CODEWITHSUNDEEP
functiondelphigenerics
user1879841
user1879841

Reputation: 23

Function Result is Generic

I need something like this:

  function fn_get_all_propperties (obj : TObject) : TObjectList<TTypeKind>;

But: [DCC Error] uFuncMain.pas(20): E2511 Type parameter 'T' must be a class type

What type should be the result of a function?

Upvotes: 1

Views: 690

Answers (1)

David Heffernan
David Heffernan

Reputation: 612794

The problem is that TObjectList is defined as follows:

TObjectList<T: class> = class(TList)
  ....
end;

The T: class in the definition means that the generic parameter T is constrained to be a class. But TTypeKind is not a class. It is a value type.

So the compiler rejects your attempted generic instantiation as being invalid because it does not satisfy the constraint.

So you cannot use TObjectList<T> here and instead should use TList<T>. Your function should be defined like this:

function fn_get_all_properties(obj: TObject): TList<TTypeKind>;

Upvotes: 2

Related Questions