Add callbacks_of_object_class_methods.dpr and check compilation of it

Author: michaliskambi

.gitignore

@@ -38,6 +38,7 @@ modern_pascal_introduction_ukrainian.xml
 /code-samples*/anon_functions_assignment_test
 /code-samples*/callbacks
 /code-samples*/callbacks_of_object
+/code-samples*/callbacks_of_object_class_methods
 /code-samples*/class_properties
 /code-samples*/constructor_destructor
 /code-samples*/exception_finally

code-samples/callbacks_of_object_class_methods.dpr

@@ -0,0 +1,33 @@
+{$ifdef FPC} {$mode objfpc}{$H+}{$J-} {$endif}
+{$ifdef MSWINDOWS} {$apptype CONSOLE} {$endif}
+
+type
+  TMyMethod = function (const A, B: Integer): Integer of object;
+
+  TMyClass = class
+    class function Add(const A, B: Integer): Integer;
+    class function Multiply(const A, B: Integer): Integer;
+  end;
+
+class function TMyClass.Add(const A, B: Integer): Integer;
+begin
+  Result := A + B;
+end;
+
+class function TMyClass.Multiply(const A, B: Integer): Integer;
+begin
+  Result := A * B;
+end;
+
+var
+  M: TMyMethod;
+begin
+  {$ifdef FPC}
+  // Unfortunately, this requires a bit of hack to work in FPC ObjFpc mode.
+  M := @TMyClass(nil).Add;
+  M := @TMyClass(nil).Multiply;
+  {$else}
+  M := TMyClass.Add;
+  M := TMyClass.Multiply;
+  {$endif}
+end.

modern_pascal_introduction.adoc

@@ -2054,23 +2054,8 @@ Note that you _cannot_ pass global procedures / functions as methods. They are i
 +
 [source,pascal]
 ----
-type
-  TMyMethod = function (const A, B: Integer): Integer of object;
-
-  TMyClass = class
-    class function Add(const A, B: Integer): Integer
-    class function Multiply(const A, B: Integer): Integer
-  end;
-
-var
-  M: TMyMethod;
-begin
-  M := @TMyClass(nil).Add;
-  M := @TMyClass(nil).Multiply;
-end;
+include::code-samples/callbacks_of_object_class_methods.dpr[]
 ----
-+
-Unfortunately, you need to write ugly `@TMyClass(nil).Add` instead of just `@TMyClass.Add`.
 
 * A (possibly) local routine: declare with `is nested` at the end, and make sure to use `{$modeswitch nestedprocvars}` directive for the code. These go hand-in-hand with <<Local (nested) routines>>.