1. 单例模式。
顾名思义， 单例模式就是只实例一次，通过一个接口去实现多处需要的同一类对象的需求。
例子：
1 ???public function __construct($config = []) 2 ????{ 3 ????????Yii::$app = $this; 4 ????????static::setInstance($this); 5 ?6 ????????$this->state = self::STATE_BEGIN; 7 ?8 ????????$this->preInit($config); 9 10 ????????$this->registerErrorHandler($config);11 12 ????????Component::__construct($config);13 ????}这是yii2应用组件容器，Appliction中的构造方法，通过构造函数，给类实现单例接口，给静态变量$app注册web应用对象。
2. 工厂模式（策略模式）。
顾名思义，工厂模式就是像工厂的机器化一样取构造当前web应用所需的类对象。
例子：
1 ????public static function createObject($type, array $params = []) 2 ????{ 3 ????????if (is_string($type)) { 4 ????????????return static::$container->get($type, $params); 5 ????????} elseif (is_array($type) && isset($type[‘class‘])) { 6 ????????????$class = $type[‘class‘]; 7 ????????????unset($type[‘class‘]); 8 ????????????return static::$container->get($class, $params, $type); 9 ????????} elseif (is_callable($type, true)) {10 ????????????return static::$container->invoke($type, $params);11 ????????} elseif (is_array($type)) {12 ????????????throw new InvalidConfigException(‘Object configuration must be an array containing a "class" element.‘);13 ????????}14 15 ????????throw new InvalidConfigException(‘Unsupported configuration type: ‘ . gettype($type));16 ????}这是yii2底层的工厂化类对象接口，通过第三方代码取实现当前web应用的工厂化模式。yii2引入的php底层预定义接口类，RefectionClass映射类，通过映射取工厂化类对象。
3. 注册模式
顾名思义，注册模式则是通过一基类接口给基类的一个全局属性，添加不同的组件对象。
例子：
1 ????public function set($id, $definition) 2 ????{ 3 ????????unset($this->_components[$id]); 4 ?5 ????????if ($definition === null) { 6 ????????????unset($this->_definitions[$id]); 7 ????????????return; 8 ????????} 9 10 ????????if (is_object($definition) || is_callable($definition, true)) {11 ????????????// an object, a class name, or a PHP callable12 ????????????$this->_definitions[$id] = $definition;13 ????????} elseif (is_array($definition)) {14 ????????????// a configuration array15 ????????????if (isset($definition[‘class‘])) {16 ????????????????$this->_definitions[$id] = $definition;17 ????????????} else {18 ????????????????throw new InvalidConfigException("The configuration for the \"$id\" component must contain a \"class\" element.");19 ????????????}20 ????????} else {21 ????????????throw new InvalidConfigException("Unexpected configuration type for the \"$id\" component: " . gettype($definition));22 ????????}23 ????}这是yii2中间类服务定位器，实现不同应用组件的注册。
1 ????public function get($id, $throwException = true) 2 ????{ 3 ????????if (isset($this->_components[$id])) { 4 ????????????return $this->_components[$id]; 5 ????????} 6 ?7 ????????if (isset($this->_definitions[$id])) { 8 ????????????$definition = $this->_definitions[$id]; 9 ????????????if (is_object($definition) && !$definition instanceof Closure) {10 ????????????????return $this->_components[$id] = $definition;11 ????????????}12 13 ????????????return $this->_components[$id] = Yii::createObject($definition);14 ????????} elseif ($throwException) {15 ????????????throw new InvalidConfigException("Unknown component ID: $id");16 ????????}17 18 ????????return null;19 ????}这是应用组件的获取。
1 ????/** 2 ?????* Returns the database connection component. 3 ?????* @return \yii\db\Connection the database connection. 4 ?????*/ 5 ????public function getDb() 6 ????{ 7 ????????return $this->get(‘db‘); 8 ????} 9 10 ????/**11 ?????* Returns the log dispatcher component.12 ?????* @return \yii\log\Dispatcher the log dispatcher application component.13 ?????*/14 ????public function getLog()15 ????{16 ????????return $this->get(‘log‘);17 ????}18 19 ????/**20 ?????* Returns the error handler component.21 ?????* @return \yii\web\ErrorHandler|\yii\console\ErrorHandler the error handler application component.22 ?????*/23 ????public function getErrorHandler()24 ????{25 ????????return $this->get(‘errorHandler‘);26 ????}27 28 ????/**29 ?????* Returns the cache component.30 ?????* @return \yii\caching\CacheInterface the cache application component. Null if the component is not enabled.31 ?????*/32 ????public function getCache()33 ????{34 ????????return $this->get(‘cache‘, false);35 ????}36 37 ????/**38 ?????* Returns the formatter component.39 ?????* @return \yii\i18n\Formatter the formatter application component.40 ?????*/41 ????public function getFormatter()42 ????{43 ????????return $this->get(‘formatter‘);44 ????}45 46 ????/**47 ?????* Returns the request component.48 ?????* @return \yii\web\Request|\yii\console\Request the request component.49 ?????*/50 ????public function getRequest()51 ????{52 ????????return $this->get(‘request‘);53 ????}54 55 ????/**56 ?????* Returns the response component.57 ?????* @return \yii\web\Response|\yii\console\Response the response component.58 ?????*/59 ????public function getResponse()60 ????{61 ????????return $this->get(‘response‘);62 ????}这是表现层Application。
4. 组装模式。
未完待续。。。。。。
PHP设计模式
原文地址：https://www.cnblogs.com/hellow-world/p/9210900.html