多次调用Eloquent动态属性是否会多次访问数据库？

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); 

现在，如果我那么做这样的事情：

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

威尔洋洋洒洒做一个数据库调用的每一次我使用->user动态属性？或者这足够聪明，可以在第一次通话时缓存用户？

Answer 1

在您的示例中，$phone对象上的user属性将被延迟加载，但只会加载一次。

请记住，一旦加载对象，它不会反映对基础表的任何更改，除非使用load方法手动重新加载关系。

下面的代码说明的例子：

$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);