各位大大：     煩請幫小弟一下，此問題有兩個地方標有●的標示。     程式由procedure TForm1.btnDetectClick(Sender: TObject);開始執行：     1●.檔程式轉移到父類別Sensor後執行到居然會自動跳過interval:=Interval，why ?     2●.當執行到IPAddress:=Target的時候程式就出現「Project prjSensor.exe raised exception class EAccessViolation with message 'Access violation at address 00403EC8 in module prjsensor.exe.......」為何會如此呢？    以上兩個問題，我已經debug好久了，都無法解決，還望各位大大教我..........    unit uIPSensor;    interface    uses   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,   Dialogs, StdCtrls, uSensor, ExtCtrls;    type     TForm1 = class(TForm)     ComboBox1: TComboBox;     btnDetect: TButton;     Memo1: TMemo;     Panel1: TPanel;     procedure btnDetectClick(Sender: TObject);   private     { Private declarations }   public     { Public declarations } end;        TIPSensor = class(TSensor) //IPSensor繼承自Sensor    private       IPAddress:string;    protected       function Detect():boolean; override;       function ShellApplication(AppName:String;AMemo:TMemo):string;    public      constructor create();      procedure IPSensor(Name,Target:string;Interval:integer);   end;    var   Form1: TForm1;   IPSensor1: TIPSensor; implementation    {$R *.dfm}    constructor TIPSensor.create; begin    inherited Create;    ShowMessage('TIPSensor.Create執行'); end;    procedure TIPSensor.IPSensor(Name,Target:string;Interval:integer); begin    ●inherited sensor(Name,Target,Interval);    ●IPAddress:=Target; end;    procedure TForm1.btnDetectClick(Sender: TObject); var Sensor:array[0..2] of TSensor; begin IPSensor1.IPSensor('PingDetect',comboBox1.Text,3); Sensor[0]:=IPSensor1.create; Sensor[0].Countdown(); end; unit uSensor; interface uses Classes,Dialogs; type TSensor = Class private timer:integer; procedure StatusChangeAlert(); protected name:string; target:string; status:boolean; interval:integer; function Detect():boolean; virtual; public constructor Create(); procedure Sensor(Name,Target:string;Interval:integer); procedure Countdown(); end; implementation constructor TSensor.Create(); begin inherited Create; ShowMessage('TSensor.Create執行'); status:=False; interval:=-1; timer:=-1; end; procedure TSensor.Sensor(Name,Target:string;Interval:integer); begin name:=Name; target:=Target; interval:=Interval; end; //end procedure

You need to create IPSenor1 first, e.g.    

{..skip..}
initialization
    IPSensor1 := TIPSensor.Create;
finalization
    IPSensor1.Free;
end;

similar in creating/freeing TIPSensor in your TForm1.btnDetectClick.

1. 試著在選單 Project-> Options-> Compiler 那一頁，把 Optimization 取消再 Compiler 一次看看 2. 看來是你根本就沒有建立 IPSensor1 的 Instance(實體)，沒有配置記憶體的變數當然沒法指定值給它.....使用前請記得先呼叫物件的 create 函式.