Question

My understanding is that the static keyword was introduced for compatibility with .NET (along with strict)

class TExample
  class procedure First;
  class procedure Second; static;

The differences between procedures First and Second are :-

1. First can be overridden in a descendant class
2. First passes an implicit self parameter referencing the TExample class.

Class procedure Second cannot be overridden and passes no parameters and is thus .NET compatible. So is there any point in using the static keyword in native-only code now that there is a divergence between Delphi & Prism syntax?

Answer 1

Static class methods have no hidden class reference argument. Because of this, they are assignment compatible with plain old function pointers, and can therefore be used for interaction with the Windows API and other C APIs. Example:

type
  TForm = class
  private
    class function NonStaticWndProc (wnd: HWND; Message: Cardinal;
      wParam: WPARAM; lParam: LPARAM): LRESULT;
    class function StaticWndProc (wnd: HWND; Message: Cardinal;
      wParam: WPARAM; lParam: LPARAM): LRESULT; static;
    procedure RegisterClass;
  end;

procedure TForm.RegisterClass;
type
  TWndProc = function (wnd: HWND; Message: Cardinal;
    wParam: WPARAM; lParam: LPARAM): LRESULT;
var
  WP: TWndProc;
  WindowClass: WNDCLASS;
begin
  //WP := NonStaticWndProc; // doesn't work
  WP := StaticWndProc; // works
  // ...
  TWndProc (WindowClass.lpfnWndProc) := WP;
  Windows.RegisterClass (WindowClass);
end;

(Of course, you could have used a global function instead, but other than global functions, static class functions have a clear association with a class.)