Classes of the Yii framework usually extend from one of the two base classes [[yii\base\Object]] and[[yii\base\Component]].
Classes of the Yii framework usually extend from one of the two base classes [[yii\base\Object]] or[[yii\base\Component]].
These classes provide useful features that are added automatically to all classes extending from them.
The [[yii\base\Object|Object]] class provides the [configuration and property feature](../api/base/Object.md).
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@@ -42,12 +42,11 @@ class MyClass extends \yii\base\Object
}
```
In the above, the last parameter of the constructor must take a configuration array
which contains name-value pairs for initializing the properties at the end of the constructor.
You can override the `init()` method to do initialization work that should be done after
the configuration is applied.
In the above example, the last parameter of the constructor must take a configuration array
which contains name-value pairs that will be used to initialize the object's properties at the end of the constructor.
You can override the `init()` method to do initialization work after the configuration is applied.
By following this convention, you will be able to create and configure a new object
By following this convention, you will be able to create and configure new objects
using a configuration array like the following:
```php
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@@ -63,13 +62,11 @@ Path Aliases
------------
Yii 2.0 expands the usage of path aliases to both file/directory paths and URLs. An alias
must start with a `@` character so that it can be differentiated from file/directory paths and URLs.
For example, the alias `@yii` refers to the Yii installation directory while `@web` contains base URL for currently
running web application. Path aliases are supported in most places in the Yii core code. For example,
`FileCache::cachePath` can take both a path alias and a normal directory path.
must start with an `@` symbol so that it can be differentiated from file/directory paths and URLs.
For example, the alias `@yii` refers to the Yii installation directory while `@web` contains the base URL for the currently running web application. Path aliases are supported in most places in the Yii core code. For example, `FileCache::cachePath` can accept both a path alias and a normal directory path.
Path alias is also closely related with class namespaces. It is recommended that a path
alias be defined for each root namespace so that you can use Yii the class autoloader without
Path aliases are also closely related to class namespaces. It is recommended that a path
alias be defined for each root namespace so that Yii's class autoloader can be used without
any further configuration. For example, because `@yii` refers to the Yii installation directory,
a class like `yii\web\Request` can be autoloaded by Yii. If you use a third party library
such as Zend Framework, you may define a path alias `@Zend` which refers to its installation
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@@ -87,28 +84,25 @@ The following aliases are predefined by the core framework:
Autoloading
-----------
All classes, interfaces and traits are loaded automatically at the moment they are used. There's no need to use
`include` or `require`. It is, as well, true for Composer-loaded packages and Yii extensions.
All classes, interfaces and traits are loaded automatically at the moment they are used. There's no need to use `include` or `require`. It is true for Composer-loaded packages as well as Yii extensions.
Autoloader works according to [PSR-4](https://github.com/php-fig/fig-standards/blob/master/proposed/psr-4-autoloader/psr-4-autoloader.md).
That means namespaces and class, interface and trait names should correspond to file system paths except root namespace
path that is defined by an alias.
Yii's autoloader works according to [PSR-4](https://github.com/php-fig/fig-standards/blob/master/proposed/psr-4-autoloader/psr-4-autoloader.md).
That means namespaces, classes, interfaces and traits must correspond to file system paths and file names accordinly, except for root namespace paths that are defined by an alias.
For example, if standard alias `@app` refers to `/var/www/example.com/` then `\app\models\User` will be loaded from
`/var/www/example.com/app/models/User.php`.
For example, if the standard alias `@app` refers to `/var/www/example.com/` then `\app\models\User` will be loaded from `/var/www/example.com/models/User.php`.
Custom alias may be added using the following code:
Custom aliases may be added using the following code:
