Design Mode notes-Observer

This mode serves as an observer to observe the Program trend. observer there are two main models:" push "and" pull ". The advantage of model pulling is that it is easy to implement and reuse. observer the model provides us with a way to let the customer program know what changes have taken place.

Which one do you want to select?ObserverThe model depends entirely on the complexity of the object to be observed. If the object to be observed is complicated and the observer needs a prompt, the push model is suitable. If the object to be observed is relatively simple, the pull model is suitable.

The key lies in abstraction, abstraction of interfaces, and abstraction of methods.