Yii2 Component基类分析

Yii2 Component类是整个Yii2 框架的基础，它重写了从Object类继承而来的getter和setter方法，主要添加的以下属性：

1. getter不止可以获取类中的属性，同时可以获取行为中的属性。

public function __get($name)
{
$getter = 'get' . $name;
if (method_exists($this, $getter)) {
// read property, e.g. getName()
return $this->$getter();
} else {
// behavior property
$this->ensureBehaviors();
foreach ($this->_behaviors as $behavior) {
if ($behavior->canGetProperty($name)) {
return $behavior->$name;
}
}
}
if (method_exists($this, 'set' . $name)) {
throw new InvalidCallException('Getting write-only property: ' . get_class($this) . '::' . $name);
} else {
throw new UnknownPropertyException('Getting unknown property: ' . get_class($this) . '::' . $name);
}
}

2. setter除了可以设置属性外，还可以设置事件和行为：

public function __set($name, $value)
{
$setter = 'set' . $name;
if (method_exists($this, $setter)) {
// set property
$this->$setter($value);

return;
} elseif (strncmp($name, 'on ', 3) === 0) {
// on event: attach event handler
$this->on(trim(substr($name, 3)), $value);

return;
} elseif (strncmp($name, 'as ', 3) === 0) {
// as behavior: attach behavior
$name = trim(substr($name, 3));
$this->attachBehavior($name, $value instanceof Behavior ? $value : Yii::createObject($value));

return;
} else {
// behavior property
$this->ensureBehaviors();
foreach ($this->_behaviors as $behavior) {
if ($behavior->canSetProperty($name)) {
$behavior->$name = $value;

return;
}
}
}
if (method_exists($this, 'get' . $name)) {
throw new InvalidCallException('Setting read-only property: ' . get_class($this) . '::' . $name);
} else {
throw new UnknownPropertyException('Setting unknown property: ' . get_class($this) . '::' . $name);
}
}

3. 覆写了__call方法，使从Component继承的类可以直接使用行为中的方法。

public function __call($name, $params)
{
$this->ensureBehaviors();
foreach ($this->_behaviors as $object) {
if ($object->hasMethod($name)) {
return call_user_func_array([$object, $name], $params);
}
}
throw new UnknownMethodException('Calling unknown method: ' . get_class($this) . "::$name()");
}

4. 其他的如isset, unset, canGetProperty, canSetProperty等辅助方法都对行为（Behavior）做了支持。