Getting a list of implemented interfaces

Frenk asked in the non-tech newsgroup:

"Is there some way to find out which interfaces (interface list) a particular component implements (I don't know [the interfaces], so querying is not possible)?"

Yes, there is.

Call TObject.GetInterfaceTable to get a pointer to the list of interfaces a specific class implements - see System.pas for details. Note that this does not include interfaces that you implement by overriding QueryInterface manually - but that is not usual for Delphi code.

For example, this code demonstrates how to dump all implementerd interfaces of a class:

program TestIntfTable;

{$APPTYPE CONSOLE}

uses
  Classes,
  SysUtils,
  TypInfo,
  ComObj;

procedure DumpInterfaces(AClass: TClass);
var
  i : integer;
  InterfaceTable: PInterfaceTable;
  InterfaceEntry: PInterfaceEntry;
begin
  while Assigned(AClass) do
  begin
    InterfaceTable := AClass.GetInterfaceTable;
    if Assigned(InterfaceTable) then
    begin
      writeln('Implemented interfaces in ', AClass.ClassName);
      for i := 0 to InterfaceTable.EntryCount-1 do
      begin
        InterfaceEntry := @InterfaceTable.Entries[i];
        writeln(Format('%d. GUID = %s',
                       [i, GUIDToString(InterfaceEntry.IID)]));
      end;
    end;
    AClass := AClass.ClassParent;
  end;
  writeln;
end;

begin
  DumpInterfaces(TComponent);
  DumpInterfaces(TComObject);
  DumpInterfaces(TComObjectFactory);
  readln;
end.

Output:

Implemented interfaces in TComponent
0. GUID = {E28B1858-EC86-4559-8FCD-6B4F824151ED}
1. GUID = {00000000-0000-0000-C000-000000000046}

Implemented interfaces in TComObject
0. GUID = {DF0B3D60-548F-101B-8E65-08002B2BD119}
1. GUID = {00000000-0000-0000-C000-000000000046}

Implemented interfaces in TComObjectFactory
0. GUID = {B196B28F-BAB4-101A-B69C-00AA00341D07}
1. GUID = {00000001-0000-0000-C000-000000000046}
2. GUID = {00000000-0000-0000-C000-000000000046}