Konsep Many-to-Many

Contoh kasus: Post bisa punya banyak Tag, dan satu Tag bisa ada di banyak Post.

Diperlukan pivot table sebagai jembatan:

posts        post_tag (pivot)    tags
id           post_id             id
title        tag_id              name

⚠️ Nama pivot table = gabungan dua nama tabel, diurutkan alfabetis, singular: post_tag

Migrasi Pivot Table

Schema::create('post_tag', function (Blueprint $table) {
    $table->foreignId('post_id')->constrained()->cascadeOnDelete();
    $table->foreignId('tag_id')->constrained()->cascadeOnDelete();
    $table->primary(['post_id', 'tag_id']); // composite primary key
});

Definisi Relasi

Model Post:

class Post extends Model
{
    public function tags(): \Illuminate\Database\Eloquent\Relations\BelongsToMany
    {
        return $this->belongsToMany(Tag::class);
    }
}

Model Tag:

class Tag extends Model
{
    public function posts(): \Illuminate\Database\Eloquent\Relations\BelongsToMany
    {
        return $this->belongsToMany(Post::class);
    }
}

Operasi Pivot

$post = Post::find(1);

// Attach: tambah relasi
$post->tags()->attach([1, 2, 3]);

// Detach: hapus relasi
$post->tags()->detach(2);

// Sync: sesuaikan relasi (hapus yang tidak ada, tambah yang baru)
$post->tags()->sync([1, 3, 5]);

// Toggle: kalau ada dihapus, kalau tidak ada ditambah
$post->tags()->toggle([2, 4]);

// Ambil semua tag dari post
$tags = $post->tags;

foreach ($tags as $tag) {
    echo $tag->name;
}

Pivot Table dengan Kolom Tambahan

Misalnya pivot menyimpan waktu role diberikan:

Schema::create('role_user', function (Blueprint $table) {
    $table->foreignId('user_id')->constrained();
    $table->foreignId('role_id')->constrained();
    $table->timestamp('assigned_at')->nullable();
    $table->primary(['user_id', 'role_id']);
});
class User extends Model
{
    public function roles(): BelongsToMany
    {
        return $this->belongsToMany(Role::class)
                    ->withPivot('assigned_at')  // sertakan kolom pivot
                    ->withTimestamps();
    }
}

// Attach dengan data pivot
$user->roles()->attach($roleId, ['assigned_at' => now()]);

// Akses data pivot
foreach ($user->roles as $role) {
    echo $role->pivot->assigned_at;
}

Ringkasan Episode 3

• Many-to-Many butuh pivot table
• Gunakan attach, detach, sync, toggle untuk kelola relasi
• withPivot() untuk akses kolom tambahan di pivot