laravel保存一對一和一對多的關係

Question

我正在創建一個應用程序，該應用程序中有一個簡單的多項選擇測驗功能。所以我有一個Question實體和一個Answer實體。我定義了2個關係，一對多（問題可以有很多答案）和一對一（問題可以有一個正確的答案）。以下是我迄今爲止：

問題型號：

class Question extends Model 
{ 
public $table = 'question'; 

public $primaryKey = 'question_id'; 

public $fillable = ['question', 'answer_id']; 

public function answers() 
{ 
    return $this->hasMany('App\Models\Answer'); 
} 

public function correctanswer() 
{ 
    return $this->hasOne('App\Models\Answer'); 
} 
} 

答型號：

class Answer extends Model 
{ 
public $table = 'answer'; 

public $primaryKey = 'answer_id'; 

public $guarded = ['created_at', 'updated_at']; 

public function question() 
{ 
    return $this->belongsTo('App\Models\Question'); 
} 

public function correctquestion() 
{ 
    return $this->belongsTo('App\Models\Question'); 
} 

} 

而且在我的控制器：

$input = $request->all(); 
    $answers = $input['answer']; 
    unset($input['answer']); 

    $question = Question::create($input); 

    foreach($answers as $key=>$a){ 
     $arr['question_id'] = $question->question_id; 
     $arr['answer'] = $a; 
     $answer = new Answer($arr); 
     $question->answers()->save($answer); //save all answers - this works 
     if($key == 0){ //the first submitted answer is the correct one 
      $question->correctanswer()->save($answer); //save correct answer - this doesn't work 
     } 
    } 

我的db表的定義：

CREATE TABLE IF NOT EXISTS question (
question_id int(11) unsigned NOT NULL AUTO_INCREMENT, 
question text, 
created_at timestamp, 
updated_at timestamp, 
answer_id int(11) unsigned, 
PRIMARY KEY (question_id), 
FOREIGN KEY (answer_id) 
    REFERENCES answer(answer_id) 
    ON DELETE NO ACTION 
    ON UPDATE NO ACTION 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; 

CREATE TABLE IF NOT EXISTS answer (
answer_id int(11) unsigned NOT NULL AUTO_INCREMENT, 
answer text, 
created_at timestamp, 
updated_at timestamp, 
question_id int(11) unsigned, 
PRIMARY KEY (answer_id), 
FOREIGN KEY (question_id) 
    REFERENCES question(question_id) 
    ON DELETE CASCADE 
    ON UPDATE CASCADE 
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; 

問題是我的問題實體沒有保存正確答案。所有的答案都在應答表中妥善保存，但我只需要做到這一點，所以我知道哪個是正確的。

任何人都可以看到我做錯了什麼？

在此先感謝！

Answer 1

事實證明，這是哪個實體擁有關係的問題。這是我改變，使其工作：

在我的問題型號：

public function correctanswer() 
{ 
    return $this->hasOne('App\Models\Answer'); 
} 

應該

public function correctanswer() 
{ 
    return $this->belongsTo('App\Models\Answer', 'answer_id', 'answer_id'); 
} 

在我的答案型號：

public function correctquestion() 
{ 
    return $this->belongsTo('App\Models\Question'); 
} 

應：

public function correctquestion() 
{ 
    return $this->hasOne('App\Models\Question'); 
} 

然後在我的控制，我只是改變了我如何救了正確答案：

$question = Question::create($input); 

    foreach($answers as $key=>$a){ 
     $arr['question_id'] = $question->question_id; 
     $arr['answer'] = $a; 
     $answer = new Answer($arr); 
     $question->answers()->save($answer); 
     if($key == 0){ 
      //$question->correctanswer()->save($answer); 
      $answer->correctquestion()->save($question); 
     } 
    } 

我不是Laravel的專家，所以我不知道爲什麼有差別。

Answer 2

嘗試改變關係的定義，像這樣，

class Question extends Model 
{ 
    public function answers() 
    { 
     return $this->hasMany('App\Models\Answer', 'question_id'); 
    } 

    public function correctanswer() 
    { 
     return $this->hasOne('App\Models\Answer', 'question_id'); 
    } 
} 

class Answer extends Model 
{ 
    public function question() 
    { 
     return $this->belongsTo('App\Models\Question', 'question_id'); 
    } 

    public function correctquestion() 
    { 
     return $this->belongsTo('App\Models\Question', 'question_id'); 
    } 
} 

由於您的主鍵沒有被命名id，你需要指定要使用的自定義鍵。