extended class syntax

static fields, static properties, regular fields and regular properties: <delphi> type

 TSomeClass = class
 private
   type
     TSomeType = type integer;    // an internal type
   class var
     FSomeClassVar: TSomeType;    // class variable belongs to a class, not an instance
   var
     FSomeIntanceVar: TSomeType;  // instance variable belongs to instance. it is a usual field
   class procedure SetSomeClassVar(const AValue: TSomeType); static;
 public
   class property SomeProperty: TSomeType read FSomeClassVar write SetSomeClassVar; // class property - belongs to a class
   property SomeInstanceProp: TSomeType read FSomeIntanceVar;
 end;

{ TSomeClass }

class procedure TSomeClass.SetSomeClassVar(const AValue: TSomeType); begin

  FSomeClassVar := AValue;

end;

var

 SomeClass: TSomeClass;

begin

 SomeClass.SomeProperty := 1;
 WriteLn(SomeClass.SomeProperty);

end. </delphi>

class constants:

<delphi> type

 TSomeClass = class
 strict private
   const
     PrivateConst = 1;
   type
     PrivateType = type Integer;
   var
     FPrivateField: PrivateType;
 public
   procedure DoSomething(Value: PrivateType = PrivateConst);
   function ReturnSomething: PrivateType;
   property SomeProp: PrivateType read FPrivateField write FPrivateField default PrivateConst;
 end;

 procedure TSomeClass.DoSomething(Value: PrivateType = PrivateConst);
 begin
 end;

 function TSomeClass.ReturnSomething: PrivateType;
 begin
   Result := PrivateConst;
 end;

begin end. </delphi>

nested classes:

<delphi> type

 TSomeClass = class
 strict private
   type
     TPrivateNestedClass = class
     public
       procedure DoSomething;
     end;
 public
   type
     TNestedClass = class
     public
       procedure DoSomething;
     end;
   class procedure Test; virtual;
 end;

 TDescendant = class(TSomeClass)
 public
   class procedure Test; override;
 end;

procedure TSomeClass.TPrivateNestedClass.DoSomething; begin

 WriteLn('TSomeClass.TPrivateNestedClass.DoSomething: ok');

end;

procedure TSomeClass.TNestedClass.DoSomething; begin

 WriteLn('TSomeClass.TNestedClass.DoSomething: ok');

end;

class procedure TSomeClass.Test; var

 P: TPrivateNestedClass;
 N: TNestedClass;

begin

 P := TPrivateNestedClass.Create;
 P.DoSomething;
 P.Free;
 N := TNestedClass.Create;
 N.DoSomething;
 N.Free;

end;

class procedure TDescendant.Test; var

 N: TNestedClass;

begin

 N := TNestedClass.Create;
 N.DoSomething;
 N.Free;

end;

begin

 TSomeClass.Test;
 TDescendant.Test;

end. </delphi>