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Attaching a watcher for every instance of a contract is not a good idea in terms of memory and CPU. So is there a way to watch for events from all instances of a contract i.e., by registering a single watcher for all instances of the contract.
Note that I don't want to provide the address of the contract instances because that will force whole DB lookup.
I need to display the changes on the contract in real-time on the client and also update the DB in real-time.
One possibility is that the contract could call a central "watcher" contract any time they wish to make a log, and then you need only watch the logs of that one contract.
To answer your question - no, unfortunately you can't capture events based on a class/contract - only on instances (addresses).
You can put in the event an indexed parameter that identifies the type of contract and then listen for events filtering on that indexed parameter.
Another way is to specify in the event as an indexed parameter your address so you can get all your contracts and then as a simple event data parameter specify the type of contract and the you can filter off chain by parsing the data part of the event.
A programmable monitoring system that ran off-chain, such as QuickBlocks can do this. QuickBlocks allows you to watch every block coming off your local node and do anything you want with it, including filter based on whatever C++ code you write to complete the filter.
