Laravel雄辩的一对一反演返回空

Question

I have following MySQL table structure:

posts table:

posts: {id(PK), title, content, slug, date, writer_id, created_at, updated_at}

writers table:

writers: {id(PK), name, type, created_at, updated_at}

Migration classes in database/migrations directory:

posts table:

class CreatePostsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('posts', function (Blueprint $table) {
            $table->increments('id');
            $table->string('title');
            $table->longText('content');
            $table->string('slug');
            $table->date('date');
            $table->date('modified_date');
            $table->integer('publish');
            $table->integer('trash');
            $table->integer('wid');
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('posts');
    }
}

Changed the type of column:

class RenamePostColumn extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('posts', function ($table) {
            $table->longText('content')->change();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('posts', function ($table) {
            $table->longText('content')->change();
        });
    }
}

Renamed a column:

class RenamePostColumnWid extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('posts', function ($table) {
            $table->renameColumn('wid', 'writer_id')->change();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('posts', function ($table) {
            $table->renameColumn('writer_id', 'wid')->change();
        });
    }
}

writers table:

class CreateWritersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('writers', function (Blueprint $table) {
            $table->increments('id');
            $table->timestamps();
            $table->string('name');
            $table->string('type');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::dropIfExists('writers');
    }
}

Following are my modals in app directory:

Post.php:

class Post extends Model
{
    public function writer()
    {
        return $this->belongsTo(Writer::class);
    }
}

Writer.php:

class Writer extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

Now I have created a repository class in app/Repositories directory.

PostRepository.php:

class PostRepository
{
    public function forSingle($slug)
    {
        return Post::whereSlug($slug)->get();
    }
}

I debugged above query with:

return Post::whereSlug($slug)->toSql();

It returns the following query:

select * from `posts` where `slug` = ?

My routes are in routes/web.php file.

web.php:

Route::get('/post/{slug}', 'PostController@single');

Finally I have my controller in app/Http/Controllers directory.

PostController.php:

use App\Repositories\PostRepository;

class PostController extends Controller
{
    protected $post;

    function __construct(PostRepository $post)
    {
        $this->post = $post;
    }

    public function single($slug)
    {
        return view('single', [
            'post' => $this->post->forSingle($slug)
        ]);
    }
}

I have rendered a view file as follows:

single.blade.php

@if (count($post) > 0)
    @foreach ($post as $blog)
        <h3><a href="#">{{$blog->title}}</a></h3>
        <p>{!!$blog->content!!}</p>
        @foreach($blog->writer as $writer)
            <span>{{$writer->name}}</span>
        @endforeach
    @endforeach
@endif

Here is my problem. Everything works fine until I add

@foreach($blog->writer as $writer)
    <span>{{$writer->name}}</span>
@endforeach

This section gives me error saying:

Trying to get property of non-object (View:\\resources\\views\\single.blade.php)

I have printed the $blog in view by {{$blog}} . It does not return any writer attribute. Can you help me with this?

PS: I have not defined primary key foreign key relationships in MySQL database tables.

Answer 1

When it is inverse one to many eloquent, we need to explicitly tell that we need the other table data. Changing following in the PostRepository.php fixed the issue.

class PostRepository
{
    public function forSingle($slug)
    {
        return Post::whereSlug($slug)->with('writer')->get();
    }
}

Answer 2

You have to define foreign key or index

In my projects, I use index relation

so what you have to do is to add index relation in writer_id like this

public function up()
{
    Schema::create('posts', function (Blueprint $table) {
        $table->increments('id');
        $table->string('title');
        $table->longText('content');
        $table->string('slug');
        $table->date('date');
        $table->date('modified_date');
        $table->integer('publish');
        $table->integer('trash');
        $table->integer('wid')->unsigned()->index(); // add this
        $table->timestamps();
    });
}

Please try the previous