如何使用__autoload从多个目录加载类? [英] How can I load classes from multiple directories with __autoload?

问题描述

在此问题之后，似乎重复的问题可能只需使用下面的__autoload代码即可解决

Following up on this question, it seems that the duplicate issue could be solved by just using the __autoload code below,

function __autoload($class_name) 
{
    include AP_SITE."classes_1/class_".$class_name.".php";
}

$connection = new database_pdo(DSN,DB_USER,DB_PASS);
var_dump($connection);

结果

object(database_pdo)[1]
  protected 'connection' => 
    object(PDO)[2]

但是这只能从一个目录加载类，而其他目录呢?因为我将类分组在不同的目录中.因此，如果我想从其他目录加载类，则会出错，

but this only loads the classes from one directory, what about other directories? Because I group the classes in different directories. So I will get error if I want to load classes from other directories,

function __autoload($class_name) 
{
    include AP_SITE."classes_1/class_".$class_name.".php";
    include AP_SITE."classes_2/class_".$class_name.".php";
}

消息

警告: 包括(C:/wamp/www/art_on_your_doorstep_2011_MVC/global/applications/CART/classes_2/class_database_pdo.php) [function.include]:无法打开流:没有这样的文件或目录 在...

Warning: include(C:/wamp/www/art_on_your_doorstep_2011_MVC/global/applications/CART/classes_2/class_database_pdo.php) [function.include]: failed to open stream: No such file or directory in ...

引用此行的

-include AP_SITE."classes_2/class_".$class_name.".php";

所以，我的问题是-如何使用__autoload从多个目录加载类?

So, my question is - how can I load classes from multiple directories with __autoload?

可能的解决方案:

function autoload_class_multiple_directory($class_name) 
{

    # List all the class directories in the array.
    $array_paths = array(
        'classes_1/', 
        'classes_2/'
    );

    # Count the total item in the array.
    $total_paths = count($array_paths);

    # Set the class file name.
    $file_name = 'class_'.strtolower($class_name).'.php';

    # Loop the array.
    for ($i = 0; $i < $total_paths; $i++) 
    {
        if(file_exists(AP_SITE.$array_paths[$i].$file_name)) 
        {
            include_once AP_SITE.$array_paths[$i].$file_name;
        } 
    }
}

spl_autoload_register('autoload_class_multiple_directory');

推荐答案

您可以使用 spl_autoload_register ，而不是单个__autoload函数.这是推荐的方法.

You can register multiple autoload functions by using spl_autoload_register instead of the single __autoload function. That's the recommended way.

如果一个自动加载器能够加载文件，则不会调用堆栈中的下一个.

If one autoloader was able to load the file, the next one in the stack won't be called.

但是，每个自动加载器仅应加载其要使用的类，因此您需要按类名和/或使用is_file进行检查.按类名通常会更好，因为如果您的应用程序增长，那么在文件系统上进行疯狂尝试会给系统造成压力.

Each autoloader however should only load the classes it is for, so you need to check that by the classname and/or with is_file. By classname often is better because trying wildly on the file-system can stress a system if your application grows.

为避免重新发明轮子，您甚至可以使用已经存在的自动加载器，该自动加载器能够在文件名调用时处理PSR-0标准.这些通常允许在基本目录上注册特定的名称空间.在您的情况下，这意味着您必须根据 PSR-0约定.

To not re-invent the wheel, you could even use an autoloader that already exists which is able to deal with the PSR-0 standard on file-name-calling. Those often allow to register a specific namespace on a base-directory. In your case that would mean that you must rename and organize your files according to the PSR-0 convention.

快速解决方案(取决于您的问题):

The quick solution (bound to your question):

function __autoload($class_name) 
{
    $file = sprintf('%sclasses_1/class_%s.php', AP_SITE, $class_name);
    if (is_file($file))
    {
        include $file;
        return;
    }
    $file = sprintf('%sclasses_2/class_%s.php', AP_SITE, $class_name);
    if (is_file($file))
    {
        include $file;
        return;
    }
}

如您所见，已经有重复的代码(如您的代码一样).因此，这应该只是一个临时解决方案，因为对于要测试的每个目录，您最终都会得到越来越多的重复行.如果您打算更改设计，请考虑PSR-0 shema，它有助于简化人的代码库，并易于重用PHP世界中的其他现有组件.

As you can see, there is already code duplicated (as in yours). So this should just be a temporary solution as you will end up with more and more duplicated lines for each directory you would like to test for. If you consider to change the design, please take the PSR-0 shema into account, it helps to streamline one's codebase and makes it easy to re-use other existing compontents in the PHP world.

function autoload_class_multiple_directory($class_name) 
{

    # List all the class directories in the array.
    $array_paths = array(
        'classes_1/', 
        'classes_2/'
    );

    foreach($array_paths as $path)
    {
        $file = sprintf('%s%s/class_%s.php', AP_SITE, $path, $class_name);
        if(is_file($file)) 
        {
            include_once $file;
        } 

    }
}

spl_autoload_register('autoload_class_multiple_directory');

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