laravel 保存一对一和一对多关系

Question

我正在创建一个应用程序，其中包含一个简单的多项选择测验功能。所以我有一个 Question 实体和一个 Answer 实体。我定义了 2 种关系，一对多（问题可以有很多答案）和一对一（问题可以有一个正确答案）。这是我目前所拥有的：

问题模型：

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');
}
}

答案模型：

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');
}

}

在我的控制器中：

    $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
        }
    }

我的数据库 table 定义：

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;

问题是我的问题实体没有保存正确答案。所有答案都正确保存在答案 table 中，但我只需要保存它，以便我知道哪个是正确的。

谁能看出我做错了什么？

提前致谢！

Answer 1

尝试像这样更改关系定义，

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');
    }
}

由于您的主键未命名 id，您需要指定您正在使用的自定义键。

Answer 2

原来是哪个实体拥有关系的问题。这是我为使它起作用所做的更改：

在我的问题模型中：

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

应该是

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

在我的答案模型中：

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

应该是：

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

然后在我的控制器中，我刚刚更改了保存正确答案的方式：

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

我还不是 Laravel 方面的专家，所以我不确定为什么会有所不同。

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