php - SQLSTATE[HY000] : General error: 1364 Field 'parent_id' doesn't have a default value

Question

我正在构建自己的论坛作为练习，我设置了具有多态关系的Topic和Comment模型，一条comment可以属于一个主题或另一个评论，这是因为我想要嵌套评论。另一个问题是当我回复该主题时出现以下错误:

SQLSTATE[HY000]: General error: 1364 Field 'parent_id' doesn't have a default value (SQL: insert into comments (user_id, body, commentable_id, commentable_type, updated_at, created_at) values (1 <\p>ljlnlnlnlnlnllnlnlnlnlnln</p>, 1, App\Models\Topic, 2019-11-08 20:41:43, 2019-11-08 20:41:43))

我的模型和迁移。

主题模型:

class Topic extends Model
{
    protected $table = 'topics';

    public function author()
    {
        return $this->belongsTo('App\Models\User', 'user_id');
    }

    public function comments()
    {
        return $this->morphMany('App\Models\Comment', 'commentable')->whereNull('parent_id');
    }
}

public function up()
{
    Schema::create('topics', function (Blueprint $table) {
        $table->increments('id');
        $table->unsignedInteger('user_id')->index();
        $table->foreign('user_id')->references('id')->on('users');
        $table->string('title');
        $table->text('body');
        $table->string('url')->unique();
        $table->string('slug')->unique();
        $table->boolean('isVisible')->default(false);
        $table->timestamps();
    });
}

评论模型:

class Comment extends Model
{
    protected $table = 'comments';

    public function author()
    {
        return $this->belongsTo('App\Models\User', 'user_id');
    }

    public function replies()
    {
        return $this->hasMany('App\Models\Comment', 'parent_id');
    }
}

public function up()
{
    Schema::create('comments', function (Blueprint $table) {
        $table->bigIncrements('id');
        $table->integer('user_id')->unsigned();
        $table->integer('parent_id')->unsigned();
        $table->integer('commentable_id')->unsigned();
        $table->string('commentable_type');
        $table->text('body');
        $table->timestamps();
    });
}

Answer 1

这个错误非常明显； parent_id 列没有值(您没有设置值，也没有默认值)。将列设置为可为空，或传递parent_id

在迁移中:

$table->integer('parent_id')->unsigned()->nullable();