Delphi: How can I know which of the indexed property has the string index using RTTI

Question

Based on some code like the following:

TListWrapper = class
  strict private
    FList: TStringList;
    function GetItem(index: Integer): TObject; overload;
    function GetItem(index: string): TObject; overload;
  public
    property Items[index: Integer]: TObject read GetItem; default;
    property Items[index: string]: TObject read GetItem; default;
end;

I want to write a piece of code which get the value of the string indexed property using RTTI. Something like this:

var
  MyList: TListWrapper;
  InstanceType: TRttiInstanceType;
  IndexedProperty: TRttiIndexedProperty;

begin
  MyList:=TListWrapper.Create;

  LContext:=TRttiContext.Create;
  InstanceType:=LContext.GetType(MyList.ClassType) as TRttiInstanceType;
  for IndexedProperty in InstanceType.GetIndexedProperties do
    if IndexedProperty.Name.ToLower = 'items' then
    begin
      //There are two indexed properties with name 'items'
    end;
  LContext.Free;
  MyList.Free;
end;

Question: How can I know which of the indexed property has the string index so that I can then get the value like this?

IndexedProperty.GetValue(MyList, ['some_string_index']);

Note: I am using Delphi 10.2.3 (Tokyo)

Answer 1

You should be able to use the read method parameters. Something like this:

readingMethod := IndexedProperty.ReadMethod;
readMethodParameters := readingMethod.GetParameters;
if readMethodParameters[0].ParamType.TypeKind = tkUString then
  // We have the string version

You should obviously check that the readMethod is assigned and that the number of parameters is greater than zero, etc.

From Remy:

In this case, the string type is tkUString (UnicodeString) and it has been this way since Delphi 2009.