Section 4: Relationship

1. One-to-one
2. One-to-many
3. Many-to-one
4. Many-to-many

You may have following relationships between your models, but following are the 3 basic steps required to setup relationship between tables.

Setup Foreign Key

Let say we want to have a user has many posts.

Create migration script:

php artisan make:migration add_post_owner --table=posts

Open up the timestamp_add_post_owner.php migration script and add the following in up and down method respectively.

Schema::table('posts', function (Blueprint $table) {
    $table->integer('user_id')->unsigned()->after('id');
});

Using after('column_name') used, in order to prevent the new column added at the end of the table columns.

Schema::table('posts', function (Blueprint $table) {
    $table->dropColumn('user_id');
});

Then we run php artisan migrate.

Update ModelFactory.php

Update the App\Post model factory by adding user_id.

$factory->define(App\Post::class, function (Faker\Generator $faker) {
    return [
        'user_id' => $faker->randomElement(range(1, 100)),
        'post' => $faker->paragraph,
    ];
});

Define Relationships in Models

Next we need to add relationship between related models, in this case we need User and Post model.

For User model, a user has many posts, add the following method app/User.php:

public function posts()
{
    return $this->hasMany('App\Post');
}

For Post model, a post belongs to user, add the following method app/Post.php:

public function user()
{
    return $this->belongsTo('App\User');
}

Usage

Once you're done setting up the relationships, you may use the models like:

$user = User::find(1);
// just dump all the posts
dd($user->posts);

$post = Post::find(1);
// echo the owner of the post
$post->user->name;