各位先進,要如何Free掉TField物件呢 我目前要對TQuery物件作動態的新增移除TField物件 新增沒問題,但是Free方面卻無法完全成功 導致runtime中再次Create Tfield物件時會導致Access Violation 我有試過下面兩種方法 MainQuery.Fields.Remove(MainQuery.FieldByName('MyField')); or MainQuery.FieldByName('MyField').Free; 但是卻沒有真正的將該TField的記憶體釋放掉 用MainQuery.FieldByName('MyField') := nil; 跟FreeAndNil(MainQuery.FieldByName('MyField')); 連編譯都不能過 會出現"Left side can not be assign to"的錯誤訊息 請各位大大指教

試試這方法

type
  TForm1 = class(TForm)
    Table1: TTable;
    Table1O001: TStringField;這是要destory的物件
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;    var
  Form1: TForm1;    implementation    {$R *.dfm}    procedure TForm1.Button1Click(Sender: TObject);
begin
Table1O001.Destroy;讓table1o001欄位destory
end;

「堅持」從洗馬桶做起 Aric

引言: 試試這方法

type
  TForm1 = class(TForm)
    Table1: TTable;
    Table1O001: TStringField;這是要destory的物件
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;    var
  Form1: TForm1;    implementation    {$R *.dfm}    procedure TForm1.Button1Click(Sender: TObject);
begin
Table1O001.Destroy;讓table1o001欄位destory
end;

「堅持」從洗馬桶做起 Aric

好像還是不太行耶 我的程式類似如下: type TForm1 = class(TForm) Table1: TTable; Table1O001: TStringField; Button1: TButton; Button2: TButton; Edit1: TEdit; procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} // Destroy TField procedure TForm1.Button1Click(Sender: TObject); begin if Table1.FindField('MyField')<>nil then Table1.FieldByName('MyField').Destroy; end; // Create TField procedure TForm1.Button2Click(Sender: TObject); var TF:TStringField; begin if Table1.FindField('MyField')=nil then begin TF := TStringField.Create(Table1); TF.Name := 'Table1MyField'; TF.FieldName := 'MyField'; TF.FieldKind := fkData; TF.DataSet := MainQuery; Table1.Fields.Add(TF); end; end; 第一次Create跟Destroy都沒問題 第二次Create竟會跳過if Table1.FindField('MyField')=nil then下的區段 表示目前Table1.FindField('MyField')<>nil 還有....為什麼TStringField不能夠使用Nil跟FreeAndNil呢?? 不是繼承TField來的嗎? 謝謝huangeider大大的回應

// Destroy TField procedure TForm1.Button1Click(Sender: TObject); var field: TField; begin field := Table1.FindField('MyField'); if field <> nil then begin Table1.Fields.Remove(field); Table2.Fields.Remove(field); field.Free; end; end;

sorry，沒有table2，是 MainQuery 才對 // Destroy TField procedure TForm1.Button1Click(Sender: TObject); var field: TField; begin field := Table1.FindField('MyField'); if field <> nil then begin Table1.Fields.Remove(field); MainQuery.Fields.Remove(field); field.Free; end; end;