Error was observed when class implements some interface.
type TDataSource = class(IGridDataSource) public ...
Compiler messages
Сообщения, предупреждений: 1 Warning: other unit files search path (aka unit path) of "Examples" contains "C:\lazarus\components\ideintf", which belongs to package "IDEIntf" Компиляция проекта, цель: bin\Examples.exe: Код завершения 1, ошибок: 3 examplesmain.pas(18,19) Error: No matching implementation for interface method "IUnknown.QueryInterface(constref TGuid,out ):LongInt; StdCall;" found examplesmain.pas(18,19) Error: No matching implementation for interface method "IUnknown._AddRef:LongInt; StdCall;" found examplesmain.pas(18,19) Error: No matching implementation for interface method "IUnknown._Release:LongInt; StdCall;" found
Solution
Add inheritance from TInterfacedObject
type TDataSource = class(TInterfacedObject, IGridDataSource) public ...