比如有一个类 Tmyclass 你创建了类的一个实列 temp:=Tmyclass.create; //判断语句 if assigned(temp)<>nil then//用assigned()判段一个指针是否为空 begin *** end;
给你两种方法的例子,你看看吧 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;
Tmyclass
你创建了类的一个实列
temp:=Tmyclass.create;
//判断语句
if assigned(temp)<>nil then//用assigned()判段一个指针是否为空
begin
***
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;