多次調用Eloquent動態屬性是否會多次訪問數據庫？

Question

http://laravel.com/docs/4.2/eloquent#dynamic-properties

class Phone extends Eloquent { 

    public function user() 
    { 
     return $this->belongsTo('User'); 
    } 

} 

$phone = Phone::find(1); 

現在，如果我那麼做這樣的事情：

echo $phone->user->email; 
echo $phone->user->name; 
echo $phone->user->nickname; 

威爾洋洋灑灑做一個數據庫調用的每一次我使用->user動態屬性？或者這足夠聰明，可以在第一次通話時緩存用戶？

Answer 1

在您的示例中，$phone對象上的user屬性將被延遲加載，但只會加載一次。

請記住，一旦加載對象，它不會反映對基礎表的任何更改，除非使用load方法手動重新加載關係。

下面的代碼說明的例子：

$phone = Phone::find(1); 

// first use of user attribute triggers lazy load 
echo $phone->user->email; 

// get that user outta here. 
User::destroy($phone->user->id); 

// echoes the name just fine, even though the record doesn't exist anymore 
echo $phone->user->name; 

// manually reload the relationship 
$phone->load('user'); 

// now will show null, since the user was deleted and the relationship was reloaded 
var_export($phone->user);