GetStrProp does not find property on object-CodePudding

I'm trying to get the properties of a TObject with their name like so:

    var key           := GetStrProp(table.Item, keyName);
    var value         := GetStrProp(table.Item, valueName);

The code above returns an error saying it cannot find property 'CODE' on the object (the keyName contains 'CODE'). The same happens for the valueName.

I tested the content of the object with the code below, it does contain the property CODE and the value also contains what I expect.

    var item          := table.Item as TdciPROJECTRESULTAATTYPE;
    var code          := item.CODE;
    var value         := item.DESCRIPTION;

What is wrong with the first 2 lines?

CodePudding user response：

There's nothing wrong with your code, but there might be something "wrong" with the TdciPROJECTRESULTAATTYPE class.

GetStrProp is one of Delphi's "old-style" RTTI methods from the TypInfo unit. The old RTTI was only generating type information for published properties of objects compiled with the {M } compiler directive (and their descendants). TdciPROJECTRESULTAATTYPE most likely does not have those old-style RTTI.

If you have a modern version of Delphi, it offers more "modern" RTTI functions(in unit RTTI), that can access way more informations about objects (Though, I don't remember at this time the exact inclusion rules). Those may allow you to access your property through RTTI.

CodePudding user response：

Thanks to Ken for pointing me in the right direction. I've created a little function that does what I need just fine. Here's the code.

class function TComboboxHelper<TTable>.GetPropertyValue(obj: TObject; name: string) : TValue;
begin
  Result              := nil;

  var rttiContext     := TRttiContext.Create;

  try
    var classType     := obj.ClassType;
    var itemType      := rttiContext.GetType(classType);
    var propType      := itemType.GetProperty(name);

    Result            := propType.GetValue(obj);

  finally
    rttiContext.Free;

  end;

end;

You can use it like so:

    var key           := GetPropertyValue(table.Item, keyName).AsString;
    var value         := GetPropertyValue(table.Item, valueName).AsString;