Unable to Add Username to Post Author - php

Question

I'm trying to insert the username for the author from the users table into the posts table, but it's not letting me. I'm using Backpack for my CRUD, and I'm not sure what I'm doing wrong. I'm also not sure as to why the ID is appearing for the username instead of the username itself, as the correct username(s) are appearing in the select box. I am getting the following error:
SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or
update a child row: a foreign key constraint fails (idf.posts,
CONSTRAINT posts_author_foreign FOREIGN KEY (author) REFERENCES
users (username)) (SQL: insert into posts (title, content,
author, updated_at, created_at) values (aasdasd, asdasda,
1, 2018-12-24 04:25:23, 2018-12-24 04:25:23))
I'm running SQL 8, Laravel 5.7, and PHP 7.1.19. So far I've tried clearing the cache via the artisan command and performing a migrate:refresh (which is fine because I have no legitimate data).
In App\Models\Post:
protected $table = 'posts';
protected $primaryKey = 'id';
protected $foreignKey = 'author';
public $timestamps = true;
protected $guarded = ['id'];
protected $fillable = [
'title', 'content', 'author'
];
protected $hidden = [];
protected $dates = [];
public function user()
{
return $this->hasOne('App\Models\User');
}
Posts Table Creation:
Schema::create('posts', function (Blueprint $table) {
$table->increments('id')->unique();
$table->string('title')->required();
$table->longtext('content')->required();
$table->string('author');
$table->foreign('author')->references('username')->on('users');
$table->timestamps();
});
Select Box on PostCrudController:
$this->crud->addField([
'label' => "Author",
'type' => 'select2',
'name' => 'author', // the db column for the foreign key
'entity' => 'user', // the method that defines the relationship in your Model
'attribute' => 'username', // foreign key attribute that is shown to user
'model' => "App\Models\User", // foreign key model
'options' => (function ($query) { //limit to only admins
return $query->orderBy('username', 'ASC')->where('admin', 1)->get();
}),
]);
In all, I just need to allow the username from the select dropdown to be inserted into the author column, which would be the username for the user itself.

Answer 1

What I understood from your problem is that you are trying to add a relation between your posts table and users.
So from my point of view, instead of using foreign migration like
$table->foreign('author')->references('username')->on('users');
you should make the foreign key like this
$table->unsignedInteger('user_id')
$table->foreign('user_id')
->references('id')
->on('users')
->onUpdate('CASCADE')
->onDelete('CASCADE');
And then you can pass the id of the user in the user_id column to establish the relationship between these two.
The benefits of using the foreign key like this are
The id column is a primary key in users table so it will uniquely Identify your user
and it is an unsigned integer so it will be easy for the SQL engine to index this.
Now for fatching your data you can definitely the following eloquent relation in your Post model
public function user() {
return $this->belongsTo('App/User');
}
And while fatching posts you can use eager loading (with() eloquent method) something like
$posts = Post:::with('user)->get();
Now with all of the posts you can access any associated user information for example:
forach ($posts as $post){
$userName = $post->user->name;
}
Hope this will help.