Delphi FDMemTable内存表用法及简单操作函数封装

红太狼 2023-10-04 19:52 32阅读 0赞

在某些场景下当轻量级的应用需要在内存中缓存数量比较多且字段比较多的高频使用数据时。以前我都是采用Ini或直接使用sqlite数据库。JSON也试过基本无法或很难实现需要的功能，因为当涉及某一同类型对象多字段多列时不通过遍历基本无法直接取到或修改数据。这样就导致了效率的低下。比如你在写一个多任务多线程并发断点续传下载工具的时候，就意味着要同时保存每个下载任务N个线程的不同状态和位置数据。并在关闭后持久化到磁盘。然后重新加载。最近发现FDMemTable真的是个好东西。非常好用。也轻量级。不像ClientDataSet还需要Midas.dll才能工作,简单记录一下

unit Unit1;
    
    interface
    
    uses
      Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
      Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ComCtrls,
      FireDAC.Stan.Intf, FireDAC.Stan.Option, FireDAC.Stan.Param,
      FireDAC.Stan.Error, FireDAC.DatS, FireDAC.Phys.Intf, FireDAC.DApt.Intf,
      Data.DB, FireDAC.Comp.DataSet, FireDAC.Comp.Client, Vcl.Grids, Vcl.DBGrids,Math
    ;
    
    type
      TForm1 = class(TForm)
        ListView1: TListView;
        Label1: TLabel;
        edtThreadCount: TEdit;
        Label2: TLabel;
        edtFileSize: TEdit;
        Button8: TButton;
        FDMemTable1: TFDMemTable;
        Button1: TButton;
        Button2: TButton;
        DBGrid1: TDBGrid;
        DataSource1: TDataSource;
        Button3: TButton;
        Label3: TLabel;
        procedure Button1Click(Sender: TObject);
        procedure Button2Click(Sender: TObject);
        procedure Button8Click(Sender: TObject);
        procedure Button3Click(Sender: TObject);
      private
        { Private declarations }
    
        {内存表操作}
        function GetIntByKey(IdkeyName:string; IdNo:Integer; KeyName:string):Integer;
        function GetStrByKey(IdkeyName:string; IdNo: Integer;KeyName:string): string;
        function SetDataByKey(IdkeyName: string; IdNo: Integer; KeyName: string; NewValue:Integer): Boolean; overload;
        function SetDataByKey(IdkeyName: string; IdNo: Integer; KeyName: string; NewValue: string): Boolean; overload;
    
    {
        function GetIntByKey(IdNo:Integer; KeyName:string):Integer;
        function GetStrByKey(IdNo: Integer;KeyName:string): string;
        function SetDataByKey(IdNo: Integer; KeyName: string; NewValue:Int64): Boolean; overload;
        function SetDataByKey(IdNo: Integer; KeyName1: string; NewValue1: Int64; KeyName2: string; NewValue2: Int64): Boolean; overload;
        function SetDataByKey(IdNo: Integer; KeyName: string; NewValue: string): Boolean; overload;
    }
      public
        { Public declarations }
      end;
    
      Const
        StartId: Integer  = 100;     //线程起始编号
        IdKey: string = 'ThreadId';  //线程编号字段名
    
    var
      Form1: TForm1;
    
    implementation
    
    {$R *.dfm}
    
    
    procedure TForm1.Button1Click(Sender: TObject);
    var
      FileSize,avg,aPos:Int64;
      ThreadCount,ThreadID,i:Integer;
    
    
    begin
      if FDMemTable1.Active then
        FDMemTable1.Close;
    
      {定义表结构}
      with FDMemTable1.FieldDefs do
      begin
        Clear;
        Add('ThreadId', ftInteger, 0, True);
        Add('Start', ftInteger, 0, True);
        Add('End', ftInteger, 0, True);
        Add('Length', ftInteger, 0, False);
        Add('Current', ftInteger, 0, False);
        Add('Status', ftInteger, 0, False);
        Add('UsedTime', ftInteger, 0, False);
        Add('LastTime', ftDateTime, 0, False);
        Add('Speed', ftFloat, 0, False);
      end;
    
      {定义索引：非必须}
      with FDMemTable1.IndexDefs do
      begin
        Clear;
        Add('Index1', 'ThreadId', []); //定义索引 正序
       //Add('Index1', 'ThreadId', [ixDescending]); //定义索引 倒序
      end;
    
      FDMemTable1.CreateDataSet;
    
       {生成测试数据}
    
     for i := 1 to 15 do
      begin
        FDMemTable1.AppendRecord([i, 1000 +i,1000 +i+100,10000,10000,0,0, Now(),58.9]);
      end;
    
    
    
    {  Json格式写法
      While aPos<FileSize do
      begin
        ThreadInfo:= TJSONObject.Create
            .AddPair('ThreadID',StartId+i)
            .AddPair('Start',aPos)
            .AddPair('End',Min(aPos+avg, FileSize-1))
            .AddPair('Length',Min(aPos+avg, FileSize-1)-aPos)
            .AddPair('Current',0)
            .AddPair('Status',0);
         JsonThread.Add(ThreadInfo);
         Inc(i);
         aPos:=aPos+avg+1;
      end;
     }
    
    
    end;
    
    procedure TForm1.Button2Click(Sender: TObject);
    var
       Item : TListItem;
    begin
       ListView1.Items.Clear;
       FDMemTable1.First;
       while (not FDMemTable1.Eof) do
          begin
             Item := ListView1.Items.Add;
             Item.Caption := FDMemTable1.fieldByName('ThreadId').AsString;
             Item.SubItems.Add(FDMemTable1.fieldByName('Start').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('End').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('Length').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('Current').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('Status').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('UsedTime').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('LastTime').AsString);
             Item.SubItems.Add(FDMemTable1.fieldByName('Speed').AsString);
    
             FDMemTable1.Next;
          end;
    
       FDMemTable1.First;
    
    end;
    
    
    {查询:返回Integer}
    function TForm1.GetIntByKey(IdkeyName: string; IdNo: Integer; KeyName: string): Integer;
    begin
      Result := 0;
      with FDMemTable1 do
      begin
        Open;
        if Locate(IdkeyName, IdNo, []) then
          Result := FieldByName(KeyName).AsInteger;
      end;
    end;
    
    {查询:返回string}
    function TForm1.GetStrByKey(IdkeyName: string; IdNo: Integer; KeyName: string): string;
    begin
      Result := '';
      with FDMemTable1 do
      begin
        Open;
        if Locate(IdkeyName, IdNo, []) then
          Result := FieldByName(KeyName).AsString;
      end;
    end;
    
    
    {修改：Integer类型}
    function TForm1.SetDataByKey(IdkeyName: string; IdNo: Integer; KeyName: string; NewValue: Integer): Boolean;
    begin
      Result := False;
      try
        with FDMemTable1 do
        begin
          Open;
          if Locate(IdkeyName, IdNo, []) then
          begin
            Edit;
            FieldByName(KeyName).AsInteger := NewValue;
            Post;
          end;
          Result := True
        end;
      except on E: Exception do
          ShowMessage(e.Message);
      end;
    end;
    
    {修改：string类型}
    function TForm1.SetDataByKey(IdkeyName: string; IdNo: Integer; KeyName: string; NewValue: string): Boolean;
    begin
      Result := False;
      try
        with FDMemTable1 do
        begin
          Open;
          if Locate(IdkeyName, IdNo, []) then
          begin
            Edit;
            FieldByName(KeyName).AsString:= NewValue;
            Post;
          end;
          Result := True
        end;
      except on E: Exception do
          ShowMessage(e.Message);
      end;
    end;
    
    procedure TForm1.Button8Click(Sender: TObject);
    var
      fld_Id: TIntegerField;
      fld_Value: TStringField;
      fld_Time: TDateTimeField;
    begin
    //  Result:=0;
      //FDMemTable1.Filter := Format('ThreadId=%d',[ID]);
      //FDMemTable1.Filtered := True;
      //Result:=FDMemTable1.FieldByName(KeyName).AsInteger
    
    //查询
    //with FDMemTable1 do
    //begin
    //Open;
    //fld_Id := TIntegerField(FieldByName('End'));
    fld_Value := TStringField(FieldByName('Value'));
    fld_Time := TDateTimeField(FieldByName('Time'));
    //if Locate('ThreadId', 12, []) then
    //ShowMessage(fld_Id.AsString);
     ShowMessage(GetIntByKey('ThreadId',108,'End').ToString);
    end;
    
    procedure TForm1.Button3Click(Sender: TObject);
    begin
      SetDataByKey('ThreadId',108,'End',8888);
    end;
    
    
    end.

测试程序效果如下：

![6860df0c13424b879c92d0a0c142b6ab.png][]

![38803000136843c582ee42efbfbd6240.png][]

**一句话总结**：**是真的很好用，轻量高效稳定!YYDS**

[6860df0c13424b879c92d0a0c142b6ab.png]: https://img-blog.csdnimg.cn/6860df0c13424b879c92d0a0c142b6ab.png
[38803000136843c582ee42efbfbd6240.png]: https://img-blog.csdnimg.cn/38803000136843c582ee42efbfbd6240.png