| Description |
The FreeAndNil procedure frees up the memory used by an object, and sets the object reference to nil.
It actually does this in reverse order - first dereferencing the object before deallocating the memory. This is a very clean way of freeing resources.
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| Related commands |
| FreeMem |
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Free memory storage used by a variable |
| GetMem |
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Get a specified number of storage bytes |
| Nil |
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A pointer value that is defined as undetermined |
| Null |
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A variable that has no value |
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| Example code : Free and nil an object, and then try to do this again |
// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.
unit Unit1;
interface
uses
SysUtils, // Unit containing the FreeAndNil command
Forms, Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm} // Include form definitions
procedure TForm1.FormCreate(Sender: TObject);
var
myList : TList;
begin
// Create the list object
myList := TList.Create;
// And now free and nil this object
FreeAndNil(myList);
// We can safely do this twice - it ignores nil objects
FreeAndNil(myList);
end;
end.
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| Hide full unit code |
No exception occurs - the second FreeAndNil does nothing.
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