有两种方法 try if form2=nil then form2:=tform2.Create(self); form2.ShowModal ; finally form2.Free; form2:=nil; end;var myobject:Tform; begin if not Assigned(form2) then begin Myobject:=tform2.Create(Self); try Myobject.ShowModal; finally Myobject.free; Myobject:=nil;//此句是必须的！ end;
...
try
if form2=nil then form2:=tform2.Create(self);
form2.ShowModal ;
finally
form2.Free;
form2:=nil;
end;var myobject:Tform;
begin
if not Assigned(form2) then
begin
Myobject:=tform2.Create(Self);
try
Myobject.ShowModal;
finally
Myobject.free;
Myobject:=nil;//此句是必须的！
end;
创建了
else
没创建