下面这段代码如何理解呢，最好在关节点上给与解释
* 行为模型实例
*
* @param string $model 模型名称
* @return obj 对象形式的返回结果
*/
function logic($model = null, $base_path = null){
static $_cache = array();
$cache_key = $model.'.'.$base_path;
if (!is_null($model) && isset($_cache[$cache_key])) return $_cache[$cache_key];
$base_path = $base_path == null ? base_data_path : $base_path;
$file_name = $base_path.'/logic/'.$model.'.logic.php';
$class_name = $model.'logic';
if (!file_exists($file_name)){
return $_cache[$cache_key] = new model($model);
}else{
require_once($file_name);
if (!class_exists($class_name)){
$error = 'logic error: class '.$class_name.' is not exists!';
throw_exception($error);
}else{
return $_cache[$cache_key] = new $class_name();
}
}
}
------解决思路----------------------
function logic($model = null, $base_path = null){
//定义静态变量
static $_cache = array();
//定义缓存key值
$cache_key = $model.'.'.$base_path;
//若是静态变量中有这个模型的实例就直接返回
if (!is_null($model) && isset($_cache[$cache_key])) return $_cache[$cache_key];
//组织类文件路径
$base_path = $base_path == null ? base_data_path : $base_path;
$file_name = $base_path.'/logic/'.$model.'.logic.php';
$class_name = $model.'logic';
//类文件是否存在
if (!file_exists($file_name)){
//不存在就实例一个model
return $_cache[$cache_key] = new model($model);
}else{
//存在就引入
require_once($file_name);
//判断是否存在 该类
if (!class_exists($class_name)){
//不存在就抛出异常
$error = 'logic error: class '.$class_name.' is not exists!';
throw_exception($error);
}else{
//存在就实例化它，存入静态数组中并返回
return $_cache[$cache_key] = new $class_name();
}
}
}