Design Pattern-Observer mode (OBSERVER)

1 Observer pattern: There are observers, then there must be a corresponding observer, the essence of the observer pattern can be summed up-when the observed changes, can timely inform the observation value, the observer can be notified after the corresponding treatment.

2 Sample Code

2.1 Defines the Observer interface, the method is that when the observer receives the notice of the Observer, the corresponding processing will be made

Obverser {change ();}

2.2 Definition of two observers

Observer1 Obverser {change () {System.    println (); }}

Observer2 Obverser {change () {System.    println (); }}

2.3 Define the observer (since to be notified, there should be a way to save the object to be notified and to add a delete notification object, which can be extended; method of notification)

Subject {notification ();    Add (Obverser obverser);        Del (Obverser Obverser); Opreation ();}

2.4 The implementation class of the observer (why it is defined here as an abstract class, because it is possible that different observers will notify different observers)

Msubject Subject {vector<obverser> =vector<obverser> ();        Notification () {enumeration<obverser> enumeration=. elements ();        (Enumeration.hasmoreelements ())        {enumeration.nextelement (). change ();    }} Add (Obverser obverser) {. Add (Obverser);    } del (Obverser obverser) {. Remove (Obverser); }}

2.5 Specific one of the observed

Msubsubject Msubject {opreation () {System..        println ();    Notification (); }}

2.6 Testing

Main {main (string[] args) {Subject subject=msubsubject ();        Subject.add (Observer1 ());        Subject.add (Observer2 ());    Subject.opreation (); }}

2.7 Test Results

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Design Pattern-Observer mode (OBSERVER)