在Yii2中输出关系数据

我试图在Yii2中输出相关数据。我的输出代码如下（就像我在Yii 1中那样）：

foreach ($model->comments as $key => $comment) {
    echo $comment->title;
}

但是我得到了错误tying to get property on a non-object，$model->comments的var_dump显示数组，看起来像什么：

    array (size=1)
  0 => 
    object(common'models'Comment)[74]
      private '_attributes' (yii'db'BaseActiveRecord) => 
        array (size=5)
          'id' => int 1
          'title' => string 'testComment' (length=11)
          'body' => string 'body' (length=4)
          'post_id' => int 1
          'user_id' => int 1
      private '_oldAttributes' (yii'db'BaseActiveRecord) => 
        array (size=5)
          'id' => int 1
          'title' => string 'testComment' (length=11)
          'body' => string 'body' (length=4)
          'post_id' => int 1
          'user_id' => int 1
      private '_related' (yii'db'BaseActiveRecord) => 
        array (size=0)
          empty

$model->getComments()的var_dump返回ActiveQuery对象：

object(yii'db'ActiveQuery)[67]
  public 'sql' => null
  public 'on' => null
  public 'joinWith' => null
  public 'select' => null
  public 'selectOption' => null
  public 'distinct' => null
  public 'from' => null
  public 'groupBy' => null
  public 'join' => null
  public 'having' => null
  public 'union' => null
  public 'params' => 
    array (size=0)
      empty
  private '_events' (yii'base'Component) => 
    array (size=0)
      empty
  private '_behaviors' (yii'base'Component) => 
    array (size=0)
      empty
  public 'where' => null
  public 'limit' => null
  public 'offset' => null
  public 'orderBy' => null
  public 'indexBy' => null
  public 'modelClass' => string 'common'models'Comment' (length=21)
  public 'with' => null
  public 'asArray' => null
  public 'multiple' => boolean true
  public 'primaryModel' => 
    object(common'models'Post)[65]
      private '_attributes' (yii'db'BaseActiveRecord) => 
        array (size=5)
          'id' => int 1
          'header' => string 'ds' (length=2)
          'content' => string 'dsad' (length=4)
          'created' => string '0000-00-00' (length=10)
          'status' => int 1
      private '_oldAttributes' (yii'db'BaseActiveRecord) => 
        array (size=5)
          'id' => int 1
          'header' => string 'ds' (length=2)
          'content' => string 'dsad' (length=4)
          'created' => string '0000-00-00' (length=10)
          'status' => int 1
      private '_related' (yii'db'BaseActiveRecord) => 
        array (size=0)
          empty
      private '_errors' (yii'base'Model) => null
      private '_validators' (yii'base'Model) => null
      private '_scenario' (yii'base'Model) => string 'default' (length=7)
      private '_events' (yii'base'Component) => 
        array (size=0)
          empty
      private '_behaviors' (yii'base'Component) => 
        array (size=0)
          empty
  public 'link' => 
    array (size=1)
      'post_id' => string 'id' (length=2)
  public 'via' => null
  public 'inverseOf' => null

我在这两种情况下都看到了我的数据，但我如何从这个结构中获得它们？（$model->getComments（）或$model->comments是wright的什么方式？）