将值分配给变量参数

function DoSomething(MyVar : Variant) : boolean;
begin
  MyVar := \'Bar\';
  Result := true;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  foo : string;
begin
  foo := \'\';
  showmessage(foo); // shows blank ofc
  DoSomething(foo);
  showmessage(foo); // still blank
end;

DoSomething(var MyVar : Variant)....

function Foo(var Bar: variant): boolean;
begin
  Bar := \'beta\';
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  a: variant;
begin
  a := \'alpha\';
  Foo(a);
  caption := a;
end;

beta

string

var variant

variant

var variant

type
  TValType = (vtString, vtInteger);
  TData = record
    ValType: TValType;
    ValStr: string;
    ValInt: integer;
  end;

function Foo(var Data: TData): boolean;