Reference object instance created using “with” in Delphi

Question

is there a way to reference an object instance that is created using the \"with\" statement?

Example:

with TAnObject.Create do
begin
  DoSomething(in         


        

Answer 1

You should never use with either because future changes might introduce more into that scope than you intended.

Take this for instance:

procedure Test;
var
    x: Integer;
begin
    with TSomeObject.Create do
    begin
        DoSomethingWithX(x);
        Free;
    end;
end;

and then later on you tuck on a X property on the TSomeObject class. Now, which X do you think it's going to use? The local variable or the X property of the object?

The best solution is always to just create a local variable with a short name, and alias the object to that variable.

procedure Test;
var
    x: Integer;
    o: TSomeObject;
begin
    o := TSomeObject.Create;
    o.DoSomethingWithX(x);
    o.Free;
end;

Answer 2

An addition to Brian's example on a Notify handler is to use an absolute variable (win32 only):

procedure Notify( Sender : TObject ); 
var 
  Something : TSomeThing absolute Sender;
begin 
  if Sender is TSomething then 
  begin
    VerySimpleProperty := Something.Something;
    OtherProperty := Something.SomethingElse;
  end;
end;

It basically avoids having to assign a local variable or have a lot of type casts.

Answer 3

for FMX, you should use GetObject example:

with TLabel.Create(box1) do
begin
    Font.Size := 34;
    Font.Style := [TFontStyle.fsBold];
    TextAlign := TTextAlign.taCenter;
    box1.AddObject(GetObject);
end;;