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How to interprete property values as textual values instead of integer (Views: 100)


Problem/Question/Abstract:

I have an application that uses RTTI to access object properties. Is it possible to interprete property values like TColor as their textual values (ie clRed) instead of an integer? Is there anything in a property's RTTI to indicate it's a type TColor and not just an integer?

Answer:

This should get you there:

unit PropertyList;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls,
    Buttons;

type
  TMyStream = class(TFileStream)
  private
    FFred: integer;
  published
    property Fred: integer read FFred write FFred;
  end;
type
  TFrmPropertyList = class(TForm)
    SpeedButton1: TSpeedButton;
    ListBox1: TListBox;
    procedure SpeedButton1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  FrmPropertyList: TFrmPropertyList;

implementation

{$R *.DFM}

uses
  TypInfo;

procedure ListProperties(AInstance: TPersistent; AList: TStrings);
var
  i: integer;
  pInfo: PTypeInfo;
  pType: PTypeData;
  propList: PPropList;
  propCnt: integer;
  tmpStr: string;
begin
  pInfo := AInstance.ClassInfo;
  if (pInfo = nil) or (pInfo^.Kind <> tkClass) then
    raise Exception.Create('Invalid type information');
  pType := GetTypeData(pInfo); {Pointer to TTypeData}
  AList.Add('Class name: ' + pInfo^.Name);
  {If any properties, add them to the list}
  propCnt := pType^.PropCount;
  if propCnt > 0 then
  begin
    AList.Add(EmptyStr);
    tmpStr := IntToStr(propCnt) + ' Propert';
    if propCnt > 1 then
      tmpStr := tmpStr + 'ies'
    else
      tmpStr := tmpStr + 'y';
    AList.Add(tmpStr);
    FillChar(tmpStr[1], Length(tmpStr), '-');
    AList.Add(tmpStr);
    {Get memory for the property list}
    GetMem(propList, sizeOf(PPropInfo) * propCnt);
    try
      {Fill in the property list}
      GetPropInfos(pInfo, propList);
      {Fill in info for each property}
      for i := 0 to propCnt - 1 do
        AList.Add(propList[i].Name + ': ' + propList[i].PropType^.Name);
    finally
      FreeMem(propList, sizeOf(PPropInfo) * propCnt);
    end;
  end;
end;

function GetPropertyList(AControl: TPersistent; AProperty: string): PPropInfo;
var
  i: integer;
  props: PPropList;
  typeData: PTypeData;
begin
  Result := nil;
  if (AControl = nil) or (AControl.ClassInfo = nil) then
    Exit;
  typeData := GetTypeData(AControl.ClassInfo);
  if (typeData = nil) or (typeData^.PropCount = 0) then
    Exit;
  GetMem(props, typeData^.PropCount * SizeOf(Pointer));
  try
    GetPropInfos(AControl.ClassInfo, props);
    for i := 0 to typeData^.PropCount - 1 do
    begin
      with Props^[i]^ do
        if (Name = AProperty) then
          result := Props^[i];
    end;
  finally
    FreeMem(props);
  end;
end;

procedure TFrmPropertyList.SpeedButton1Click(Sender: TObject);
var
  c: integer;
begin
  ListProperties(self, ListBox1.Items);
  for c := 0 to ComponentCount - 1 do
  begin
    ListBox1.Items.Add(EmptyStr);
    ListProperties(Components[c], ListBox1.Items);
  end;
end;

end.

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