Detailed explanation of service locator pattern examples of PHP design patterns

Service locator (service locator) knows how to locate (create or obtain) the services required by an application. Service users do not need to care about the actual implementation of the service in actual use. This article mainly shares with you a detailed explanation of the service locator pattern example of PHP design pattern. I hope it can help you.

What is the role

To achieve the decoupling of service users and services, there is no need to change the code but only by simply configuring and updating the service.

UML diagram

##Code sample

class ServiceLocator {

    /**
     * 服务实例索引
     */
    privite $_services = [];

    /**
     * 服务定义索引
     */
    private $_definitions = [];
    
    /**
     * 是否全局服务共享（单例模式）
     */
    private $_shared = [];
    
    public function has($id){
        return isset($this->_services[$id]) || isset($this->_definitions[$id]);
    }
    
    public function __get($id){
        if($this->has($this->id)){
            $this->get($id);
        }
        
        // another implement
    }
    
    public function get($id){
        if(isset($this->_services[$id]) && $this->_shared[$id]){
            return $this->_services[$id];
        }
        
        if (isset($this->_definitions[$id])) {
            // 实例化
            $definition = $this->_definitions[$id];
            $object = Creator::createObject($definition);//省略服务实例化实现
            if($this->_shared[$id]){
                $this->_services[$id] = $object
            }
            
            return $object;
        }
        
        throw new Exception("无法定位服务{$id}")
    }
        
    public function set($id,$definition,$share = false){
        if ($definition === null) {
            unset($this->_services[$id], $this->_definitions[$id]);
            return;
        }
        
        unset($this->_services[$id]);
        $this->_shared[$id] = $share;
        if (is_string($definition)) {
            return $this->_definitions[$id] = $definition;
        }
        if (is_object($definition) || is_callable($definition, true)) {
            return $this->_definitions[$id] = $definition;
        }
        
        if (is_array($definition)) {
            if (isset($definition['class'])) {
                return $this->_definitions[$id] = $definition;
            }
        }
        
        throw new Exception("服务添加失败");
    }
}

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