获得每个相关模型的最大值与雄辩的Laravel [英] get max value for each related model with eloquent in laravel

问题描述

我有2个模型：

class Message extends Eloquent {

    public function conversation(){
        return $this->belongsTo('Conversation', 'conversationId');
    }


    public function sender(){
        return $this->belongsTo('User', 'senderId')->select('id', 'userName');
    }


    public function receiver(){
        return $this->belongsTo('User', 'receiverId')->select('id', 'userName');
    }
}

class DeskConversation extends Eloquent {

}

我想要的是采取每个会话的所有最后的消息（包括在给定的数组中）...换句话说，我想采取一些对话，并为每个他们只有最后一个消息被交换了。

What I want is to take all the last messages of each conversation (those included in a given array)... in other words I would like to take some conversations and, for each of them, only the last message that was exchanged.

我可以通过以下方式获取所有给定对话的所有消息：

I'm able to get all the messages for all the given conversation with this:

return Message::whereHas('conversation', function($query) use ($convIds) {
    $query->whereIn('id', $convIds);
})->with('sender')->with('receiver')->orderBy('conversationId')->orderBy('id', 'DESC')->get();

其中 $ convIds 是一组ids

每个会话中只有最后一条消息如何？

How to take, for each conversation, only the last message?

推荐答案

这是您需要的：

/**
 * Conversation has one latest Message
 *
 * @return Illuminate\Database\Eloquent\Relations\HasOne
 */
public function latestMessage()
{
    return $this->hasOne('Message')->latest();
}

然后只是：

$conversations = Conversation::with('latestMessage')->get();
// then each latest message can be accessed:
$conversation->latestMessage;
$conversations->first()->latestMessage;

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