Laravel 13 Eloquent 改进详解

摘要

Laravel 13 对 Eloquent ORM 进行了多项改进，包括访问器、修改器和关系定义的增强。本文将深入讲解 Laravel 13 的 Eloquent 改进，包括：

  • 访问器与修改器新语法
  • 属性转换增强
  • 关系定义改进
  • 查询优化
  • 实战案例与最佳实践

本文适合希望掌握 Laravel 13 Eloquent 新特性的开发者。

1. 访问器与修改器

1.1 访问器

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<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Casts\Attribute;

class User extends Model
{
    protected function fullName(): Attribute
    {
        return Attribute::make(
            get: fn($value, $attributes) => $attributes['first_name'] . ' ' . $attributes['last_name'],
        );
    }
    
    protected function avatar(): Attribute
    {
        return Attribute::make(
            get: fn($value) => $value ?? 'default-avatar.png',
        );
    }
}

1.2 修改器

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class User extends Model
{
    protected function password(): Attribute
    {
        return Attribute::make(
            set: fn($value) => bcrypt($value),
        );
    }
    
    protected function email(): Attribute
    {
        return Attribute::make(
            set: fn($value) => strtolower($value),
        );
    }
}

1.3 访问器与修改器组合

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class User extends Model
{
    protected function name(): Attribute
    {
        return Attribute::make(
            get: fn($value) => ucfirst($value),
            set: fn($value) => strtolower($value),
        );
    }
}

1.4 属性缓存

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class User extends Model
{
    protected function expensiveComputation(): Attribute
    {
        return Attribute::make(
            get: fn($value) => $this->computeExpensiveValue(),
        )->shouldCache();
    }
}

2. 属性转换

2.1 基本转换

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class User extends Model
{
    protected $casts = [
        'is_admin' => 'boolean',
        'options' => 'array',
        'settings' => 'collection',
        'created_at' => 'datetime',
        'expires_at' => 'date',
    ];
}

2.2 枚举转换

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enum Status: string
{
    case Draft = 'draft';
    case Published = 'published';
    case Archived = 'archived';
}

class Post extends Model
{
    protected $casts = [
        'status' => Status::class,
    ];
}

// 使用
$post->status = Status::Published;
echo $post->status->value; // 'published'

2.3 加密转换

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class User extends Model
{
    protected $casts = [
        'secret' => 'encrypted',
        'api_key' => 'encrypted',
    ];
}

2.4 自定义转换

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<?php

namespace App\Casts;

use Illuminate\Contracts\Database\Eloquent\CastsAttributes;

class Json implements CastsAttributes
{
    public function get($model, string $key, $value, array $attributes)
    {
        return json_decode($value, true);
    }
    
    public function set($model, string $key, $value, array $attributes)
    {
        return json_encode($value);
    }
}

class Post extends Model
{
    protected $casts = [
        'metadata' => Json::class,
    ];
}

3. 关系定义

3.1 一对一

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class User extends Model
{
    public function profile()
    {
        return $this->hasOne(Profile::class);
    }
}

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

3.2 一对多

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

class Post extends Model
{
    public function author()
    {
        return $this->belongsTo(User::class, 'author_id');
    }
}

3.3 多对多

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class User extends Model
{
    public function roles()
    {
        return $this->belongsToMany(Role::class)
            ->withPivot('assigned_at')
            ->withTimestamps();
    }
}

class Role extends Model
{
    public function users()
    {
        return $this->belongsToMany(User::class);
    }
}

3.4 多态关系

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class Post extends Model
{
    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
    
    public function tags()
    {
        return $this->morphToMany(Tag::class, 'taggable');
    }
}

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo();
    }
}

4. 查询优化

4.1 延迟加载

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// N+1 问题
$posts = Post::all();
foreach ($posts as $post) {
    echo $post->author->name; // 每次查询
}

4.2 预加载

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// 解决 N+1
$posts = Post::with('author')->get();
foreach ($posts as $post) {
    echo $post->author->name; // 不额外查询
}

4.3 嵌套预加载

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$posts = Post::with(['author', 'comments.user'])->get();

4.4 条件预加载

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$posts = Post::with(['comments' => function ($query) {
    $query->where('approved', true);
}])->get();

4.5 懒加载

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$posts = Post::all();
$posts->load('author', 'comments');

5. 模型事件

5.1 事件监听

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class User extends Model
{
    protected static function booted()
    {
        static::creating(function ($user) {
            $user->api_token = Str::random(60);
        });
        
        static::updating(function ($user) {
            if ($user->isDirty('email')) {
                $user->email_verified_at = null;
            }
        });
    }
}

5.2 观察者

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<?php

namespace App\Observers;

use App\Models\User;

class UserObserver
{
    public function created(User $user)
    {
        // 用户创建后
    }
    
    public function updated(User $user)
    {
        // 用户更新后
    }
    
    public function deleted(User $user)
    {
        // 用户删除后
    }
}

// 注册观察者
use App\Models\User;
use App\Observers\UserObserver;

User::observe(UserObserver::class);

5.3 属性观察者

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use Illuminate\Database\Eloquent\Attributes\ObservedBy;

#[ObservedBy(UserObserver::class)]
class User extends Model
{
    // 自动注册观察者
}

6. 实战案例

6.1 完整模型示例

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<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Casts\Attribute;
use Illuminate\Database\Eloquent\Relations\HasMany;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;
use Illuminate\Database\Eloquent\Attributes\ObservedBy;
use App\Observers\UserObserver;
use App\Enums\UserStatus;

#[ObservedBy(UserObserver::class)]
class User extends Model
{
    protected $fillable = [
        'name',
        'email',
        'password',
        'status',
        'settings',
    ];
    
    protected $hidden = [
        'password',
        'remember_token',
    ];
    
    protected $casts = [
        'status' => UserStatus::class,
        'settings' => 'array',
        'email_verified_at' => 'datetime',
    ];
    
    protected function password(): Attribute
    {
        return Attribute::make(
            set: fn($value) => bcrypt($value),
        );
    }
    
    protected function avatar(): Attribute
    {
        return Attribute::make(
            get: fn($value) => $value 
                ? Storage::url($value) 
                : asset('images/default-avatar.png'),
        );
    }
    
    public function posts(): HasMany
    {
        return $this->hasMany(Post::class, 'author_id');
    }
    
    public function roles(): BelongsToMany
    {
        return $this->belongsToMany(Role::class)
            ->withTimestamps();
    }
    
    public function scopeActive($query)
    {
        return $query->where('status', UserStatus::Active);
    }
    
    public function scopeAdmins($query)
    {
        return $query->whereHas('roles', fn($q) => $q->where('name', 'admin'));
    }
}

7. 最佳实践

7.1 模型命名

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// 推荐：单数形式
User
Post
Comment

// 不推荐
Users
Posts
Comments

7.2 关系命名

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// 推荐：描述性命名
public function publishedPosts()
public function recentComments()

// 不推荐
public function posts2()
public function commentsNew()

8. 总结

Laravel 13 的 Eloquent 改进提供了更强大的模型定义能力：

  1. 访问器/修改器：简洁的属性定义
  2. 属性转换：支持枚举和自定义转换
  3. 关系定义：灵活的关系类型
  4. 查询优化：预加载解决 N+1

参考资料