如何在Laravel中使用雄辩

创建模型和迁移：使用 php artisan make:model Post -m 生成模型和迁移文件，定义表结构后运行 php artisan migrate；2. 基本CRUD操作：通过 Post::all()、find()、create()、save() 和 delete() 方法实现数据的查询、创建、更新和删除；3. 使用Eloquent关联：在模型中定义 belongsTo 和 hasMany 关系，并通过 with() 方法实现关联数据的预加载以避免N 1查询问题；4. Eloquent查询：利用查询构造器链式调用如 where、orderBy 等方法，并通过局部作用域 scopePublished 复用查询逻辑；5. 批量赋值保护：在模型中设置 $fillable 或 $guarded 属性以防止意外赋值；6. 软删除：引入 SoftDeletes trait 并在迁移中添加 softDeletes()，使用 delete() 和 restore() 控制软删除与恢复；7. 访问器与修改器：通过 setTitleAttribute 和 getTitleAttribute 在设置或获取属性时自动处理数据格式。Eloquent通过模型与数据库交互，使开发者无需编写原生SQL即可高效操作数据，建议每张表对应一个模型，合理定义关联关系并充分利用Eloquent提供的功能完成数据操作，最终实现清晰、可维护的代码结构。

Eloquent is Laravel’s built-in ORM (Object-Relational Mapper) that makes it easy to interact with your database using PHP syntax instead of writing raw SQL. It’s powerful, expressive, and beginner-friendly once you understand the basics. Here’s how to use Eloquent effectively in Laravel.

1. Creating Models and Migrations

Every database table has a corresponding Eloquent model. To create a model along with a migration, run:

php artisan make:model Post -m

This creates:

• app/Models/Post.php (the model)
• database/migrations/xxxx_xx_xx_create_posts_table.php (the migration)

In the migration file, define your table structure:

Schema::create('posts', function (Blueprint $table) {
    $table->id();
    $table->string('title');
    $table->text('content');
    $table->foreignId('user_id')->constrained();
    $table->timestamps();
});

Run the migration:

php artisan migrate

Now you can use the Post model to interact with the posts table.

Note: If your model is in a folder like Models, make sure to reference it correctly or update the default namespace in config/auth.php if needed.

2. Basic CRUD Operations

Once your model is set up, you can perform basic operations.

Retrieve All Records

$posts = Post::all();

Find a Record by ID

$post = Post::find(1);
// or throw an exception if not found
$post = Post::findOrFail(1);

Create a New Record

Post::create([
    'title' => 'My First Post',
    'content' => 'Hello World',
    'user_id' => 1,
]);

Or manually:

$post = new Post();
$post->title = 'Another Post';
$post->content = 'More content';
$post->user_id = 1;
$post->save();

Update a Record

$post = Post::find(1);
$post->title = 'Updated Title';
$post->save();

Or use mass update:

Post::where('id', 1)->update(['title' => 'Updated']);

Delete a Record

$post = Post::find(1);
$post->delete();

// or delete directly
Post::destroy(1);

3. Using Eloquent Relationships

Eloquent makes defining relationships between models simple.

Define a Relationship (e.g., Post belongs to User)

In the Post model:

public function user()
{
    return $this->belongsTo(User::class);
}

In the User model:

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

Now you can access related data:

$post = Post::with('user')->find(1);
echo $post->user->name; // Access the author

$user = User::find(1);
foreach ($user->posts as $post) {
    echo $post->title;
}

Use with() to eager load relationships and avoid N 1 query problems.

4. Querying with Eloquent

Eloquent models extend the query builder, so you can chain methods:

$publishedPosts = Post::where('status', 'published')
    ->where('created_at', '>', now()->subDays(7))
    ->orderBy('created_at', 'desc')
    ->get();

Scopes (Reusable Queries)

Define a local scope in your model:

public function scopePublished($query)
{
    return $query->where('status', 'published');
}

Use it:

$posts = Post::published()->get();

5. Mass Assignment Protection

To use create() or update() safely, define fillable or guarded fields.

In your model:

protected $fillable = ['title', 'content', 'user_id'];

Or, alternatively:

protected $guarded = []; // allows all, but less secure

6. Soft Deletes (Optional)

To "delete" records without removing them from the database:

• Add use Illuminate\Database\Eloquent\SoftDeletes; to your model.
• Add $table->softDeletes(); in your migration.
• Then use ->delete() — it sets deleted_at instead of removing the row.

Restore a soft-deleted record:

$post = Post::withTrashed()->find(1);
$post->restore();

7. Accessors and Mutators

Modify data when getting or setting attributes.

Mutator (set)

public function setTitleAttribute($value)
{
    $this->attributes['title'] = ucfirst($value);
}

Accessor (get)

public function getTitleAttribute($value)
{
    return ucfirst($value);
}

Now every time you get or set title, it's capitalized.

Eloquent makes working with databases in Laravel intuitive and clean. Start with models and basic queries, then gradually use relationships, scopes, and accessors as your app grows. Most of the time, you won’t need raw SQL.

Basically, just remember: one model per table, define relationships, and let Eloquent do the heavy lifting.

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