namespace app\components;

use yii\base\Behavior;

class MyBehavior extends Behavior
{
  public $prop1;

  private $_prop2;

  public function getProp2()
  {
    return $this->_prop2;
  }

  public function setProp2($value)
  {
    $this->_prop2 = $value;
  }

  public function foo()
  {
    // ...
  }
}

namespace app\models;

use yii\db\ActiveRecord;
use app\Components\MyBehavior;

class User extends ActiveRecord
{
  public function behaviors()
  {
    return [
      // 匿名的行为，仅直接给出行为的类名称
      MyBehavior::className(),

      // 名为myBehavior2的行为，也是仅给出行为的类名称
      'myBehavior2' => MyBehavior::className(),

      // 匿名行为，给出了MyBehavior类的配置数组
      [
        'class' => MyBehavior::className(),
        'prop1' => 'value1',
        'prop3' => 'value3',
      ],

      // 名为myBehavior4的行为，也是给出了MyBehavior类的配置数组
      'myBehavior4' => [
        'class' => MyBehavior::className(),
        'prop1' => 'value1',
        'prop3' => 'value3',
      ]
    ];
  }
}

[
  'as myBehavior2' => MyBehavior::className(),

  'as myBehavior3' => [
    'class' => MyBehavior::className(),
    'prop1' => 'value1',
    'prop3' => 'value3',
  ],
]

$Component->attachBehaviors([
  'myBehavior1' => new MyBehavior, // 这是一个命名行为
  MyBehavior::className(),     // 这是一个匿名行为
]);

$behavior = $Component->getBehavior('myBehavior2');

$behaviors = $Component->getBehaviors();

yii\base\Component::behaviors()
yii\base\Component::ensureBehaviors()
yii\base\Component::attachBehaviorInternal()
yii\base\Behavior::attach()

public function ensureBehaviors()
{
  // 为null表示尚未绑定
  // 多说一句，为空数组表示没有绑定任何行为
  if ($this->_behaviors === null) {
    $this->_behaviors = [];

    // 遍历 $this->behaviors() 返回的数组，并绑定
    foreach ($this->behaviors() as $name => $behavior) {
      $this->attachBehaviorInternal($name, $behavior);
    }
  }
}

private function attachBehaviorInternal($name, $behavior)
{
  // 不是 Behavior 实例，说是只是类名、配置数组，那么就创建出来吧
  if (!($behavior instanceof Behavior)) {
    $behavior = Yii::createObject($behavior);
  }

  // 匿名行为
  if (is_int($name)) {
    $behavior->attach($this);
    $this->_behaviors[] = $behavior;

  // 命名行为
  } else {

    // 已经有一个同名的行为，要先解除，再将新的行为绑定上去。
    if (isset($this->_behaviors[$name])) {
      $this->_behaviors[$name]->detach();
    }
    $behavior->attach($this);
    $this->_behaviors[$name] = $behavior;
  }
  return $behavior;
}

public function attach($owner)
{
  $this->owner = $owner;
  foreach ($this->events() as $event => $handler) {
    $owner->on($event, is_string($handler) ? [$this, $handler] :
      $handler);
  }
}