源码procedure TObject.Free; begin if Self <> nil then Destroy; end;
Disposes of an object instance.Delphi syntax:destructor Destroy; virtual;DescriptionDo not call Destroy directly. Call Free instead. Free verifies that the object reference is not nil before calling Destroy.The Destroy method defined by TObject deallocates memory. Descendant objects usually define a destructor that is customized for that particular kind of object.When declaring a Destroy method in a descendant, always add the override directive to the declaration and call the inherited Destroy as the last statement in the overriding method. Since Destroy is a virtual method, overriding it ensures that the proper inherited behavior occurs.Note: If an exception escapes from the constructor, the destructor is called to destroy the partially constructed object instance that failed to initialize completely. Therefore, destructors should check that allocated resources, such as handles, were actually allocated before trying to release them, since their value might be zero.Destroy should be implemented so that it calls Free on all subobjects created within the object's constructor (that is, allocated by the constructor). Unlike Destroy, Free provides a safeguard when destroying objects that are nil.
在程序代码中，要使用Free。当写ＶＣＬ代码时，可以使用Destroy;
procedure TObject.Free; begin if Self <> nil then Destroy; end;
Destroy必须是它的对像不为nil
begin
if Self <> nil then
Destroy;
end;
begin
if Self <> nil then
Destroy;
end;