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The SplObserver interface

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

简介

The SplObserver interface is used alongside SplSubject to implement the Observer Design Pattern.

接口摘要

interface SplObserver {
/* 方法 */
public update(SplSubject $subject): void
}

目录

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User Contributed Notes 2 notes

up
107
aiddroid at example dot com
10 years ago
<?php

/**
* Subject,that who makes news
*/
class Newspaper implements \SplSubject{
private
$name;
private
$observers = array();
private
$content;

public function
__construct($name) {
$this->name = $name;
}

//add observer
public function attach(\SplObserver $observer) {
$this->observers[] = $observer;
}

//remove observer
public function detach(\SplObserver $observer) {

$key = array_search($observer,$this->observers, true);
if(
$key){
unset(
$this->observers[$key]);
}
}

//set breakouts news
public function breakOutNews($content) {
$this->content = $content;
$this->notify();
}

public function
getContent() {
return
$this->content." ({$this->name})";
}

//notify observers(or some of them)
public function notify() {
foreach (
$this->observers as $value) {
$value->update($this);
}
}
}

/**
* Observer,that who recieves news
*/
class Reader implements SplObserver{
private
$name;

public function
__construct($name) {
$this->name = $name;
}

public function
update(\SplSubject $subject) {
echo
$this->name.' is reading breakout news <b>'.$subject->getContent().'</b><br>';
}
}

$newspaper = new Newspaper('Newyork Times');

$allen = new Reader('Allen');
$jim = new Reader('Jim');
$linda = new Reader('Linda');

//add reader
$newspaper->attach($allen);
$newspaper->attach($jim);
$newspaper->attach($linda);

//remove reader
$newspaper->detach($linda);

//set break outs
$newspaper->breakOutNews('USA break down!');

//=====output======
//Allen is reading breakout news USA break down! (Newyork Times)
//Jim is reading breakout news USA break down! (Newyork Times)
up
98
sebastien dot ferrandez at free dot fr
10 years ago
Beware, you have written :

if($key){
unset($this->observers[$key]);
}

When this should be :

if(false !== $key){
unset($this->observers[$key]);
}

If the observer you want to delete is the first in your array, you will never delete it because the key would equal 0 and 0 == false as you know.
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