Author: KK Gian Gian

How can I prevent resources leak.

Answer:

Make use of Interface characteristic where when the reference goes out of scope it 
will free itself.

1   type
2     IAutoClean = interface
3       ['{61D9CBA6-B1CE-4297-9319-66CC86CE6922}']
4     end;
5   
6     TAutoClean = class(TInterfacedObject, IAutoClean)
7     private
8       FObj: TObject;
9     public
10      constructor Create(AObj: TObject);
11      destructor Destroy; override;
12    end;
13  
14  implementation
15  
16  constructor TAutoClean.Create(AObj: TObject);
17  begin
18    FObj := AObj;
19  end;
20  
21  destructor TAutoClean.Destroy;
22  begin
23    FreeAndNil(FObj);
24    inherited;
25  end;
26  
27  Application....
28  
29  procedure TForm1.Button1Click(Sender: TObject);
30  var
31    a: IAutoClean;
32      //must declare as local variable, so when this procedure finished, it's out of 
33  scope
34    o: TOpenDialog; //any component
35  begin
36    o := TOpenDialog.Create(self);
37    a := TAutoClean.Create(o);
38    if o.Execute then
39      ShowMessage(o.FileName);
40  end;