Hello all! Today I’m writing another technical post about how message broadcasting is done in Gaff/Shibboleth. The high level idea isn’t very complicated: Listeners are registered as either functions, member functions, or functors. When a listener registers themselves, they are returned a “receipt”. When this receipt is released, it will automatically unregister the listener. While this adds some extra memory usage from having to store all these receipts, the end user no longer needs to remember to unregister manually!