TeardownLogic

This interface describes what should be returned by function passed to Observable constructor or static create function. Value of that interface will be used to cancel subscription for given Observable.

TeardownLogic can be:

Function

Function that takes no parameters. When consumer of created Observable calls unsubscribe, that function will be called

AnonymousSubscription

AnonymousSubscription is simply an object with unsubscribe method on it. That method will work the same as function

void

If created Observable does not have any resources to clean up, function does not have to return anything.