Question

我正在尝试构建一个消息传递系统。我有多个用户和多对话的对话。

用户模型：

public function conversations() {
    return $this->belongsToMany('Conversation');
}

会话

public function users() {
    return $this->belongsToMany('User');
}

我可以获得用户和用户所在的对话：

$user = User::with('conversations')->find(Auth::user()->id);

或者：

$user = User::with('conversations')->find(1);

问题是，当用户没有任何对话时，我得到一个例外：

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error 
in your SQL syntax; check the manual that corresponds to your MySQL server 
version for the right syntax to use near ')' at line 1 (SQL: select * from 
`conversations` where `id` in ()) (Bindings: array ( ))

如何测试用户是否有对话以避免这种情况？提前谢谢。

编辑：

我在ConversationsController中创建了新的对话，如下所示：

在David Barker的解决方案后更新了创建方法：

public function create($id)
{
    // Check user exists
    $user = User::find($id);
    if ( ! $user )
        throw new Exception('User not found');

    // Create a new conversation
    $conversation = new Conversation();
    $conversation->creator = Auth::user()->id;
    $conversation->save();

    // Attach the users to the conversation
    $conversation->users()->attach($user);
    $conversation->users()->attach(Auth::user());

    return $conversation;
}

但我仍然以这种方式获得例外。

离开项目几个小时后，我认为这可能是一个可能的解决方案：

$con = User::find(Auth::user()->id)->conversations; 

if(0 < $con->count()) {

    $conversationIds = array();
    foreach ($con as $conversation) {
        $conversationIds[] = $conversation->id;
    }

    // I THINK THIS WAS ACTUALLY THE PROBLEM
    $conversations = Conversation::with('users')->whereIn('id', $conversationIds)->get();

} else {
    $conversations = false;
}

Answer 1

在您的班级用户上，添加您的关系：

class User extends Eloquent implements UserInterface, RemindableInterface {

    function conversations(){
        return $this->hasMany('Conversation'); 
        //assuming you have a conversation model too
    }

}

然后你可以这样做：

$conversations = Auth::user()->conversations;

或找到具体的ID：

$conversations = User::find($id)->conversations;

并且您将拥有附加到当前用户的所有会话。
在你得到对话之后......你可以在做任何其他事情之前检查它是否为空。
（例如：if(0 < $conversations->count()){ }）

您可以在laravel docs

上找到更多信息

<强>更新

你可以试试这个吗？

$user = User::has('conversation')->where('user.id','=', $id)->get();

更新2：

// get all the conversations connected to the current user
$my_conversations = Auth::user()->conversations;

// generate a list of all the conversation ids 
foreach($my_conversations as $my_conversation) {
    $conversation_ids[] = $my_conversation->id;
}

if(!empty($conversation_ids)) {
    // get all the users for each conversations, via eager loading
    $conversations = Conversation::with('User')
        ->whereIn('id', $conversation_ids)->get();
}

Answer 2

目前您不允许Eloquent管理跨关系的数据插入。 Eloquent非常容易管理，最好让它为你做这件事，看起来它可能是你问题的根源。

public function create($id)
{
    // Use the logged in user or the passed in user ID for user object
    $user = isset($id) ? User::find($id) : Auth::user();

    // Check user exists
    if ( ! $user )
        throw new Exception('User not found');

    // Create a new conversation
    $conversation = new Conversation(array(
        'creator' => $user->id
    ));

    $conversation->save();

    // Attach the user model to the conversation
    // this method will insert all of the relational
    // information into the pivot table for you
    $conversation->users()->attach($user);

    return $conversation;
}

当没有记录匹配时，Laravel 4多对多关系错误

2 个答案: