96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
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# 类的加载
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Kohana 需要使用 PHP 自身的[自动加载](http://php.net/manual/language.oop5.autoload.php)。这个消除了不用调用 [include](http://php.net/include) 和 [require](http://php.net/require) 之前就可以使用类文件。例如，让你想使用 [Cookie::set] 方法时，你只需要：
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Cookie::set('mycookie', 'any string value');
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或者要加载一个 [Encrypt] 的实例化，只需要调用 [Encrypt::instance]：
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$encrypt = Encrypt::instance();
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类也可以通过 [Kohana::auto_load] 方法加载，这使得从简单的类名称转换为文件名：
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1. 类必须放置在[文件系统](start.filesystem)的 `classes/` 目录
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2. 任何下划线字符转换为斜线
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2. 文件名必须是小写的
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当调用一个尚未加载类（比如，`Session_Cookie`），通过使用 [Kohana::find_file] 方法可以让 Kohana 搜索文件系统查找名为 `classes/session/cookie.php` 的文件。
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## 自动加载器
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在 `application/bootstrap.php` 配置文件默认使用 [spl_autoload_register](http://php.net/spl_autoload_register) 开启了自动加载器。
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spl_autoload_register(array('Kohana', 'auto_load'));
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在此类第一次使用的时候，这让 [Kohana::auto_load] 尝试去加载任意的不存在类。
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# Transparent Class Extension {#class-extension}
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The [cascading filesystem](about.filesystem) allows transparent class extension. For instance, the class [Cookie] is defined in `SYSPATH/classes/cookie.php` as:
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class Cookie extends Kohana_Cookie {}
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The default Kohana classes, and many extensions, use this definition so that almost all classes can be extended. You extend any class transparently, by defining your own class in `APPPATH/classes/cookie.php` to add your own methods.
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[!!] You should **never** modify any of the files that are distributed with Kohana. Always make modifications to classes using extensions to prevent upgrade issues.
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For instance, if you wanted to create method that sets encrypted cookies using the [Encrypt] class:
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<?php defined('SYSPATH') or die('No direct script access.');
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class Cookie extends Kohana_Cookie {
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/**
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* @var mixed default encryption instance
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*/
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public static $encryption = 'default';
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/**
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* Sets an encrypted cookie.
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*
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* @uses Cookie::set
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* @uses Encrypt::encode
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*/
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public static function encrypt($name, $value, $expiration = NULL)
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{
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$value = Encrypt::instance(Cookie::$encrpytion)->encode((string) $value);
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parent::set($name, $value, $expiration);
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}
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/**
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* Gets an encrypted cookie.
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*
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* @uses Cookie::get
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* @uses Encrypt::decode
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*/
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public static function decrypt($name, $default = NULL)
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{
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if ($value = parent::get($name, NULL))
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{
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$value = Encrypt::instance(Cookie::$encryption)->decode($value);
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}
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return isset($value) ? $value : $default;
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}
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} // End Cookie
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Now calling `Cookie::encrypt('secret', $data)` will create an encrypted cookie which we can decrypt with `$data = Cookie::decrypt('secret')`.
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## Multiple Levels of Extension {#multiple-extensions}
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If you are extending a Kohana class in a module, you should maintain transparent extensions. Instead of making the [Cookie] extension extend Kohana, you can create `MODPATH/mymod/encrypted/cookie.php`:
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class Encrypted_Cookie extends Kohana_Cookie {
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// Use the same encrypt() and decrypt() methods as above
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}
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And create `MODPATH/mymod/cookie.php`:
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class Cookie extends Encrypted_Cookie {}
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This will still allow users to add their own extension to [Cookie] with your extensions intact. However, the next extension of [Cookie] will have to extend `Encrypted_Cookie` instead of `Kohana_Cookie`.
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