数据缓存中的依赖关系

1、缓存文件依赖

1  $cache = YII::$app->cache;
2         $dependency = new yiicachingFileDependency(['fileName'=>'hw.txt']);
3         $cache->add('file_key','hello world',3000,$dependency);
4         var_dump($cache->get('file_key'));

当hw.txt文件中的内容出现变化，则该缓存过期

2、表达式依赖：

1 $cache = YII::$app->cache;
2         $dependency = new yiicachingExpressionDependency(['expression'=>'YII::$app->request->get("name")']);
3         $cache->add('expression_key','hello world',3000,$dependency);
4         var_dump($cache->get('expression_key'));

当 ['expression'=>'YII::$app->request->get("name")'] 中获得的name的值发生了变化，则缓存过期

3、DB依赖

1 $cache=YII::$app->cache;
2         $dependency = new yiicachingDbDependency(
3             ['sql'=>'SELECT count(*) FROM yii.order']
4         );
5         $cache->add('db_key','hello_world',3000,$dependency);
6         var_dump($cache->get('db_key'));