delphi 如何保存属性到运行期使用(上)|笨鱼技术网

Most of use a table or some kind of files to store the data for the application to pick up the data during run time. Actually we can store the data in the form file ( dfm ). In the following example I have created a component derived from the TPersistent class. It uses the TReader and TWriter class to Read and write to the respective streams. The TComponentEditor allows to define the design time editors to work with the component class. The TPropertyEditor class allows to define a property editor for a specialized property in a component class.

In the following example I have given the component's source code. The design time property editor has a source file code(pas) and source form code for the form (dfm). copy the dfm code to create a dfm file, name it as "propdlg.dfm" and assign it's Name property to "fmpropdlg" and the source file code to create a pas file, name it as "propdlg.pas". Install the component TMyComponent, include the file "propdlg.pas" of the property editor in the the package.

The component will then allow you to invoke the design time editor by clicking on the object inspector for the specified property or by right clicking on the component itself and then selecting the respective verb in the menu context. You can store the fields of the class Tmydata in the form file ( dfm ) during design time.

//**********************************************************************
//***** Component source (pas) *****************************************
//**********************************************************************
unit Test;

interface

uses
Windows, Forms, Classes, StdCtrls, SysUtils, ComCtrls, Messages, Controls,
{DB, DBCtrls, CommCtrl, OCIH, OCI, OCL, ExtVCs,} dsgnintf;

type
TMyPropertyEditor = class(TPropertyEditor)
private
    { Private declarations }
public
    { Public declarations }
    function GetAttributes: TPropertyAttributes; override;
    procedure Edit; override;
    function GetValue: string; override;
end;

TMyEditorPopup = class(TComponentEditor)
private
    { Private declarations }
public
    { Public declarations }
    procedure Edit; override;
    procedure ExecuteVerb(Index: Integer); override;
    function GetVerb(Index: Integer): string; override;
    function GetVerbCount: Integer; override;
end;

TMyData = class
private
    Fstr: string;
    FInt: Integer;
public
    property StringValue: string read Fstr write FStr;
    property IntegerValue: Integer read FInt write FInt;
end;

TMyTable = class(TPersistent)
private
    FList: TList;
    function GetCount: Integer;
    function GetItem(Index: Integer): TMyData;

    procedure SetItem(Index: Integer; vItem: TMyData);
    procedure ReadProperties(Reader: TReader);
    procedure WriteProperties(Writer: TWriter);
protected
    procedure DefineProperties(Filer: TFiler); override;
public
    constructor Create;
    destructor Destroy; override;
    procedure AddItem;
    procedure DeleteItem(Index: Integer);
    property ItemCount: Integer read GetCount;
    property Items[Index: Integer]: TMyData read GetItem write SetItem; default;
end;

TMyComponent = class(TComponent)
private
    FMyTable: TMyTable;
    procedure SetTables(Value: TMyTable);
public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
published
    property MyTables: TMyTable read FMyTable write SetTables;
end;

procedure Register;

implementation

uses PropDlg;
{ TMyTable }

constructor TMyTable.Create;
begin
FList := TList.Create;
FList.Clear;
end;

destructor TMyTable.Destroy;
begin
FList.Free;
FList := nil;
inherited destroy;
end;

procedure TMyTable.DefineProperties(Filer: TFiler);
begin
Filer.DefineProperty('Tables', ReadProperties, WriteProperties, True);
end;

procedure TMyTable.ReadProperties(Reader: TReader);
begin
Reader.ReadListBegin;
while (not Reader.EndOfList) do
begin
    AddItem;
    with Items[itemCount - 1] do
    begin
      Fstr := Reader.ReadString;
      FInt := Reader.ReadInteger;
    end;
end;
Reader.ReadListEnd;
end;

procedure TMyTable.WriteProperties(Writer: TWriter);
var
I: Integer;
begin
Writer.WriteListBegin;
for I := 0 to (ItemCount - 1) do
begin
    with Items[I] do
    begin
      Writer.WriteString(Fstr);
      Writer.WriteInteger(FInt);
    end;
end;
Writer.WriteListEnd;
end;

procedure TMyTable.AddItem;
var
vData: TMyData;
begin
vData := TMyData.Create;
FList.Add(vData);
end;

function TMyTable.GetCount: Integer;
begin
Result := FList.Count;
end;

function TMyTable.GetItem(Index: Integer): TMyData;
begin
Result := TMyData(FList[Index]);
end;

procedure TMyTable.SetItem(Index: Integer; vItem: TMyData);
begin
Flist[Index] := vItem;
end;

procedure TMyTable.DeleteItem(Index: Integer);
begin
FList.Delete(Index);
end;