Laravel 4：在嵌套关系中，我如何热切加载和检索第一个/最后一个数据？ [英] Laravel 4 : In nested relationship, how do I eager load and retrieve just the first/last data?
问题描述
B：对话，
C：消息
我想与A中的A-> B-> C关系得到对话与最新消息
模型中的工作关系
用户属于多对话
对话belongsToMany用户
对话有多个消息
消息属于对话
用户hasMany消息
消息属于用户
**注意：用户和对话与many2many有关关系连接
由枢轴表
我尝试了
$ user-> load（['conversations'=> function（$ q）
{
$ q-> orderBy（'created_at'，'desc'）;
$ q-> with（'Messages'） - > orderBy（'created_at'，'desc'）;
}]）;
它几乎工作，但没有得到最后的消息。
上述代码的不需要的结果
array（size = 7）
'id'=> int 90
'name'=> string'haha，hehe'（length = 9）
'created_at'=> string'2014-07-03 15:04:04'（length = 19）
'updated_at'=> string'2014-07-03 15:04:04'（length = 19）
'microseconds'=> string'1404370893302'（length = 13）
'pivot'=>
array（size = 2）
'user_id'=> int 1
'conversations_id'=> int 90
'messages'=>
array（size = 27）
0 =>
...
1 =>
...
...
26 =>
array（size = 7）
'id'=> int 816
'user_id'=> int 1
'conv_id'=> int 90
'body'=> string'test1'（length = 5）
'created_at'=> string'2014-07-03 01:13:35'（length = 19）
'updated_at'=> string'2014-07-03 01:13:35'（length = 19）
'microseconds'=>字符串'1404350015499'（length = 13）
预期结果
array（size = 7）
'id'=> int 90
'name'=> string'haha，hehe'（length = 9）
'created_at'=> string'2014-07-03 15:04:04'（length = 19）
'updated_at'=> string'2014-07-03 15:04:04'（length = 19）
'microseconds'=> string'1404370893302'（length = 13）
'pivot'=>
array（size = 2）
'user_id'=> int 1
'conversations_id'=> int 90
'messages'=>
array（size = 1）
0 =>
array（size = 7）
'id'=> int 816
'user_id'=> int 1
'conv_id'=> int 90
'body'=> string'test1'（length = 5）
'created_at'=> string'2014-07-03 01:13:35'（length = 19）
'updated_at'=> string'2014-07-03 01:13:35'（length = 19）
'microseconds'=> string'1404350015499'（length = 13）
将获得（或首先 / 找到等）在闭包中，它再次运行查询，但是该查询被忽略，然后Eloquent再次执行该查询：
$ user-> load（['conversations'=> function（$ q）
{
$ q-> orderBy（'created_at'，'desc'）;
$ q- > with（'Messages'） - > orderBy（'created_at'，'desc'）
- > get（）//此查询在这里执行
- > first（）; / /这调用第一个方法收集
//但上述2行对于eager负载模型
//不起作用，因为Eloquent将在最后执行查询
}]） ;
这是你如何对嵌套关系进行约束（但不会在这里工作）：
User :: with（['conversations.messages'=> function ）{
$ q-> orderBy（...） - > where（...）...;
//但限制（1）不能在这里使用
}]） - > get（）;
限制不能使用，因为它将整个设置限制为1，因此总共只返回1个消息。也就是说，只有1个对话将在一个集合中加载单个消息。完全错误
所以唯一的这个帮助者关系的方式可以实现这一点：
//对话模型
public function latestMessage（）
{
return $ this-> hasOne（'Message'） - > latest（）;
}
//然后简单地：
$ user-> load（'conversations.latestMessage'）;
$ user-> conversations-> first（） - > latestMessage; //单个消息模型
A : User,
B : Conversations,
C : Messages
I want to get the conversation together with it's most recent message in an A->B->C relationship from A.
Working relationships in model
User belongsToMany Conversation
Conversation belongsToMany User
Conversation hasMany Message
Message belongsTo Conversation
User hasMany Message
Message belongsTo User
**note: User and Conversation are related to a many2many relationship connected
by a pivot table
I've tried
$user->load(['conversations' => function($q)
{
$q->orderBy('created_at', 'desc');
$q->with('Messages')->orderBy('created_at','desc');
}]);
It nearly worked but it doesn't get the last message. Instead, it loads all of the messages belonging to that conversation.
Unwanted result from above code
array (size=7)
'id' => int 90
'name' => string 'haha,hehe' (length=9)
'created_at' => string '2014-07-03 15:04:04' (length=19)
'updated_at' => string '2014-07-03 15:04:04' (length=19)
'microseconds' => string '1404370893302' (length=13)
'pivot' =>
array (size=2)
'user_id' => int 1
'conversations_id' => int 90
'messages' =>
array (size=27)
0 =>
...
1 =>
...
...
26 =>
array (size=7)
'id' => int 816
'user_id' => int 1
'conv_id' => int 90
'body' => string 'test1' (length=5)
'created_at' => string '2014-07-03 01:13:35' (length=19)
'updated_at' => string '2014-07-03 01:13:35' (length=19)
'microseconds' => string '1404350015499' (length=13)
Expected result
array (size=7)
'id' => int 90
'name' => string 'haha,hehe' (length=9)
'created_at' => string '2014-07-03 15:04:04' (length=19)
'updated_at' => string '2014-07-03 15:04:04' (length=19)
'microseconds' => string '1404370893302' (length=13)
'pivot' =>
array (size=2)
'user_id' => int 1
'conversations_id' => int 90
'messages' =>
array (size=1)
0 =>
array (size=7)
'id' => int 816
'user_id' => int 1
'conv_id' => int 90
'body' => string 'test1' (length=5)
'created_at' => string '2014-07-03 01:13:35' (length=19)
'updated_at' => string '2014-07-03 01:13:35' (length=19)
'microseconds' => string '1404350015499' (length=13)
When you put get (or first/find etc for that matter) in the closure it runs the query once more, but that query is ignored, and then Eloquent executes that query again:
$user->load(['conversations' => function($q)
{
$q->orderBy('created_at', 'desc');
$q->with('Messages')->orderBy('created_at','desc')
->get() // this query is executed here
->first(); // this calls first method on the collection
// but those 2 lines above take no effect with the eager load models
// because Eloquent will execute the query again in the end
}]);
This is how you put constraints on the nested relation (but it won't do the job here):
User::with(['conversations.messages' => function ($q) {
$q->orderBy(...)->where(...) ...;
// but limit(1) can't be used here
}])->get();
Limit can't be used because it limits the whole set to 1, so there will be only 1 message returned in total. That said, only 1 conversation will have loaded single message in a collection.. Totally wrong
So the only way to achieve this with Eloquent is this 'helper' relation:
// Conversation model
public function latestMessage()
{
return $this->hasOne('Message')->latest();
}
// then simply:
$user->load('conversations.latestMessage');
$user->conversations->first()->latestMessage; // single Message model
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