Question

Error: Types of actual and formal var parameters must be identical

unit unAutoKeypress;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    Memo2: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
procedure SimulateKeyDown(Key:byte);
begin
keybd_event(Key,0,0,0);
end;

procedure SimulateKeyUp(Key:byte);
begin
keybd_event(Key,0,KEYEVENTF_KEYUP,0);
end;

procedure doKeyPress(var KeyValue:byte);
begin
 SimulateKeyDown(KeyValue);
 SimulateKeyUp(KeyValue);
end;



procedure TForm1.Button1Click(Sender: TObject);
const test = 'merry Christmas!';
var m: byte;
begin
Memo2.SetFocus();
m:=$13;
doKeyPress(m); // THIS IS WHERE ERROR
end;

end.

always error in function doKeyPress(m);
a simple question, why?

I know something wrong with types, but all types are similar, everywhere is byte, strange
for me and I cant run a program.

Answer 1

The problem is that doKeyPress is a method of TForm1 (inherited from TWinControl) and so when you write doKeyPress inside a TForm1 method the compiler wants to use TForm1.doKeyPress rather than the local function. The class scope is nearer than the local function scope.

Possible solutions include:

• Renaming the local function to avoid the clash.
• Using a fully qualified name, unAutoKeypress.doKeyPress.

The former is a better solution in my opinion.