mirror of
https://github.com/yiisoft/yii2.git
synced 2025-11-04 06:37:55 +08:00
86 lines
2.9 KiB
Markdown
86 lines
2.9 KiB
Markdown
Basic concepts of Yii
|
|
=====================
|
|
|
|
|
|
Component and Object
|
|
--------------------
|
|
|
|
Classes of the Yii framework usually extend from one of the two base classes [[Object]] and [[Component]].
|
|
These classes provide useful features that are added automatically to all classes extending from them.
|
|
|
|
The `Object` class provides the [configuration and property feature](../api/base/Object.md).
|
|
The `Component` class extends from `Object` and adds [event handling](events.md) and [behaviors](behaviors.md).
|
|
|
|
`Object` is usually used for classes that represent basic data structures while `Component` is used for
|
|
application components and other classes that implement higher logic.
|
|
|
|
|
|
Object Configuration
|
|
--------------------
|
|
|
|
The [[Object]] class introduces a uniform way of configuring objects. Any descendant class
|
|
of [[Object]] should declare its constructor (if needed) in the following way so that
|
|
it can be properly configured:
|
|
|
|
```php
|
|
class MyClass extends \yii\base\Object
|
|
{
|
|
public function __construct($param1, $param2, $config = [])
|
|
{
|
|
// ... initialization before configuration is applied
|
|
|
|
parent::__construct($config);
|
|
}
|
|
|
|
public function init()
|
|
{
|
|
parent::init();
|
|
|
|
// ... initialization after configuration is applied
|
|
}
|
|
}
|
|
```
|
|
|
|
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.
|
|
|
|
By following this convention, you will be able to create and configure a new object
|
|
using a configuration array like the following:
|
|
|
|
```php
|
|
$object = Yii::createObject([
|
|
'class' => 'MyClass',
|
|
'property1' => 'abc',
|
|
'property2' => 'cde',
|
|
], $param1, $param2);
|
|
```
|
|
|
|
|
|
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.
|
|
|
|
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
|
|
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
|
|
directory and Yii will be able to autoload any class in this library.
|
|
|
|
|
|
Autoloading
|
|
-----------
|
|
|
|
TBD
|
|
|
|
Helper classes
|
|
--------------
|
|
|
|
TDB |