Delphi 实现类的转形，将类定义为可用和不可用：
procedure TForm1.SetEnable(Enable: Boolean);
var
i:Integer;
begin
for i:=0 to Self.ComponentCount-1 do
begin
if Self.Components[i] is TEdit then
(Self.Components[i] as TEdit).Enabled := Enable;
end;
end;
定义类可用：
procedure TForm1.Bu
