最近做了一些事情，其中一件就是分离出之前基于CI写的Service层并打包发布到GitHub。
想着还是应该留下一点什么，便是来由。
这是还在Yumeer的时候，那会儿江哥刚来，梳理了整个业务逻辑，发现杂乱无章，遂推倒了重来。还是我一人负责后端，囿于经验，之前完全是hard-coding，代码复用性基本为0，加之CI的特性：

-The Model represents your data structures. Typically your model classes will contain functions that help you retrieve, insert, and update information in your database.
-The View is the information that is being presented to a user. A View will normally be a web page, but in CodeIgniter, a view can also be a page fragment like a header or footer. It can also be an RSS page, or any other type of “page”.
-The Controller serves as an intermediary between the Model, the View, and any other resources needed to process the HTTP request and generate a web page.

导致大量business logic堆积到Controller层甚至Model层，着实难看。后面江哥提出一个想法，做Microservice，了解过后，准备开做。
CI的简洁易用性出于此，麻烦也同出于此。由于Controller层无法互相调用，在设计模式上，只能通过新构建一层架于C-M之间。本着面向Google/Stackoverflow编程的原则（手动滑稽），先找了找，发现了一些思路和代码片段。遂开始仔细分析。
CI提供了极其灵活的扩展接口，分析过后，找到一条路，简而言之就是通过对core的扩展，增加一层类似于library层的独立层，同样使用原生load进行加载。

核心代码：

// The service layer core
public function service($service = '', $params = NULL, $object_name = NULL)
{
    if (is_array($service)) {
        foreach ($service as $class) {
            $this->service($class, $params);
        }
        return $this;
    }
    if ($service == '' or isset($this->_ci_services[$service])) {
        return FALSE;
    }
    if (!is_null($params) && !is_array($params)) {
        $params = NULL;
    }
    $subdir = '';

// Is the service in a sub-folder? If so, parse out the filename and path.
    if (($last_slash = strrpos($service, '/')) !== FALSE) {
// The path is in front of the last slash
        $subdir = substr($service, 0, $last_slash + 1);
// And the service name behind it
        $service = substr($service, $last_slash + 1);
    }
    foreach ($this->_ci_service_paths as $path) {
        $filepath = $path . 'services/' . $subdir . $service . '.php';
        if (!file_exists($filepath)) {
            continue;
        }
        include_once($filepath);
        $service = strtolower($service);
        if (empty($object_name)) {
            $object_name = $service;
        }
        $service = ucfirst($service);
        $CI =& get_instance();
        if ($params !== NULL) {
            $CI->$object_name = new $service($params);
        } else {
            $CI->$object_name = new $service();
        }
        $this->_ci_services[] = $object_name;
        return $this;
    }
}

// Extend load
class MY_Service
{
    public function __construct()
    {
        log_message('debug', "Service Class Initialized");
    }
    function __get($key)
    {
        $CI =& get_instance();
        return $CI->$key;
    }
}

 

Flowchart：
待补
GitHub：
acerest/ServiceLayer4CodeIgniter
欢迎Star ：）