Laravel 4多對多關係錯誤，當沒有記錄匹配

Question

我試圖建立一個消息系統。我有哪些用戶和對話有多對多的關係。

用戶模式：

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

對話

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

我能得到用戶和通話用戶與：

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

或者：

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

的問題是，當用戶沒有任何交談，我得到一個例外：

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 ()) 

如何測試用戶是否有對話，以避免這種情況？提前致謝。

編輯：

我創建的ConversationsController新的對話，像這樣：

更新後，大衛·巴克的解決方案的創建方法：

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; 
} 

但我仍然得到例外這種方式也。

從幾個小時我覺得這可能是一個可能的解決方案的項目走開後：

$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

在你的類用戶，添加您的關係：

class User extends Eloquent implements UserInterface, RemindableInterface { 

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

} 

，那麼你可以這樣做而不是：

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

或查找特定ID：

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

，你必須附加到當前用戶的所有對話..
你已經拿到了交談後..你可以檢查它是否在做任何事情之前空..
（例如：if(0 < $conversations->count()){ } ）

你可以在這裏找到更多的信息對laravel docs

---

UPDATE：

你可以試試這個嗎？

$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

此刻你是不是讓雄辯管理整個關係數據的插入。雄辯地管理這件事非常容易，最好讓它爲你做這件事，這看起來可能是你的問題的根源。

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; 
}