Observer Mode (SUBJECT/OBSERVER)

Definition: A one-to-many dependency between objects, and when the state of an object changes, all objects that depend on it are notified and automatically updated.

Function: Search the database and send it in various ways when there is a need to publish the data.

The observer model can certainly be very good to achieve the above requirements, no matter how many ways, as long as the addition of multiple inherited Itransfer interface of the derived classes can be very good maintenance.

The following are practical applications.