20个Laravel Eloquent 使用技巧

转载自 Laravel-news

1、自增、自减

    //常规写法
    $article = Article::find($article_id);
    $article->read_count++;
    $article->save();
    
    //eloquent写法-1
    $article = Article::find($article_id);
    $article->increment('read_count');
    
    //eloquent写法-2 链式写法
    Article::find($article_id)->increment('read_count');
    Article::find($article_id)->increment('read_count', 10); // +10
    Product::find($produce_id)->decrement('stock'); // -1

2、条件式方法 XorY methods

• findOrFail(): 查询不到的时候直接报错

    $user = User::find($id);
    if (!$user) { abort (404); }
    //以上代码等同于
    $user = User::findOrFail($id);

• firstOrCreate():使用给定的字段及其值在数据库中查找记录。如果在数据库中找不到模型，则将使用第一个参数中的属性以及可选的第二个参数中的属性插入记录

    // 通过 name 属性检索航班，当结果不存在时创建它...
    $flight = App\Flight::firstOrCreate(['name' => 'Flight 10']);

    // 通过 name 属性检索航班，当结果不存在的时候用 name 属性和 delayed 属性去创建它
    $flight = App\Flight::firstOrCreate(
        ['name' => 'Flight 10'], ['delayed' => 1]
    );

• firstOrNew():用法和firstOrCreate()一样，但是firstOrNew()只是实例化一个对象，如果需要持久化则需要save()保存
• updateOrCreate(): 更新现有模型或创建新模型（如果不存在）,同firstOrCreate()

3、Model类boot()方法

    /**
     * 基类：新增的时候自动将`uuid`字段用`Uuid`生成器填充
     */
    class BaseModel extends Model
    {
        public static function boot()
        {
            parent::boot();
            self::creating(function ($model) {
                $model->uuid = (string)Uuid::generate();
            });
        }
    }
    
    /**
     * 用户模型：修改的时候设置额外的操作
     */
    class User extends BaseModel
    {
        public static function boot()
        {
            parent::boot();
            static::updating(function($model)
            {
                // do some logging
                // override some property like $model->something = transform($something);
            });
        }
    }

4、关联添加额外条件并设置排序Relationship with conditions and ordering

    //通常的做法，关联用户模型
    public function users() {
        return $this->hasMany('App\User');    
    }

    //关联已经批准并用`email`排序的用户模型
    public function approvedUsers() {
        return $this->hasMany('App\User')->where('approved', 1)->orderBy('email');
    }

5、Model类属性 Model properties: timestamps, appends etc.

    class User extends Model {
        //经常用到的属性
        protected $table = 'users';
        protected $fillable = ['email', 'password']; // which fields can be filled with User::create()
        protected $dates = ['created_at', 'deleted_at']; // which fields will be Carbon-ized
        protected $appends = ['field1', 'field2']; // additional values returned in JSON
        
        //其他很有用的属性
        protected $primaryKey = 'uuid'; // it doesn't have to be "id"
        protected $keyType = 'string'; //设置主键字段类型 default `int`
        public $incrementing = false; // and it doesn't even have to be auto-incrementing!
        protected $perPage = 25; // Yes, you can override pagination count PER MODEL (default 15)
        const CREATED_AT = 'created_at';
        const UPDATED_AT = 'updated_at'; // Yes, even those names can be overridden
        public $timestamps = false; // or even not used at all
    }

6、用find方法查找多条记录Find multiple entries

    //find常用用法
    $user = User::find(1);
    //find其实也接收 数组 为参数
    $users = User::find([1,2,3]);

7、whereX魔术方法

    //where字段名：字段名第一字母大写
    $users = User::whereApproved(1)->get(); //等同于 $users = User::where('approved', 1)->get();
    User::whereDate('created_at', date('Y-m-d'));
    User::whereDay('created_at', date('d'));
    User::whereMonth('created_at', date('m'));
    User::whereYear('created_at', date('Y'));

8、Order by relationship

场景：论坛很多帖子topic，需要按有最新发言post的来排序

    //帖子关联最新的发言
    public function latestPost()
    {
        return $this->hasOne(\App\Post::class)->latest();
    }
    $users = Topic::with('latestPost')->get()->sortByDesc('latestPost.created_at');

9、Eloquent::when()别再写那么多的if-else

    //通常的写法
    if (request('filter_by') == 'likes') {
        $query->where('likes', '>', request('likes_amount', 0));
    }
    if (request('filter_by') == 'date') {
        $query->orderBy('created_at', request('ordering_rule', 'desc'));
    }
    
    //Eloquent::when()写法
    $query = Author::query();
    $query->when(request('filter_by') == 'likes', function ($q) {
        return $q->where('likes', '>', request('likes_amount', 0));
    });
    $query->when(request('filter_by') == 'date', function ($q) {
        return $q->orderBy('created_at', request('ordering_rule', 'desc'));
    });
    //可以传递参数
    $query = User::query();
    $query->when(request('role', false), function ($q, $role) { 
        return $q->where('role_id', $role);
    });
    $authors = $query->get();

10、BelongsTo Default Models

    //blade:如果 author 被删了就会报错
    {{ $post->author->name }}
    
    //设置 缺省Model 避免以上错误
    public function author()
    {
        return $this->belongsTo('App\Author')->withDefault([
            'name' => 'Guest Author'
        ]);
    }

11、Order by Mutator ： 借助集合collect->sortBy方法

    function getFullNameAttribute()
    {
      return $this->attributes['first_name'] . ' ' . $this->attributes['last_name'];
    }
    //错误写法
    $clients = Client::orderBy('full_name')->get(); // doesn't work
    //正确写法，借助collect的sortBy方法
    $clients = Client::get()->sortBy('full_name'); // works!

12、Default ordering in global scope

    protected static function boot()
    {
        parent::boot();
    
        // Order by name ASC
        static::addGlobalScope('order', function (Builder $builder) {
            $builder->orderBy('name', 'asc');
        });
    }

13、 Raw query methods

    // whereRaw
    $orders = DB::table('orders')
        ->whereRaw('price > IF(state = "TX", ?, 100)', [200])
        ->get();
    
    // havingRaw
    Product::groupBy('category_id')->havingRaw('COUNT(*) > 1')->get();
    
    // orderByRaw
    User::where('created_at', '>', '2016-01-01')
      ->orderByRaw('(updated_at - created_at) desc')
      ->get();

14、Replicate: make a copy of a row

这是复制某条记录最好的方法

    $task = Tasks::find(1);
    $newTask = $task->replicate();
    $newTask->save();

15、Chunk() method for big tables

Collect集合方法：需要输出大量记录的时候用chunk

    User::chunk(100, function ($users) {
        foreach ($users as $user) {
            // ...
        }
    });

16、Create additional things when creating a model

用artisan命令生成model的时候一起生成controller -r、migration file

    php artisan make:model Company -mcr

17、Override updated_at when saving

save()方法接收额外的参数

    $product = Product::find($id);
    $product->updated_at = '2019-01-01 10:00:00';
    $product->save(['timestamps' => false]);

18、What is the result of an update()?

    //返回更新的记录数
    $result = $products->whereNull('category_id')->update(['category_id' => 2]);

19、where参数分组

    //... WHERE (gender = 'Male' and age >= 18) or (gender = 'Female' and age >= 65) 的 Eloquent 写法
    $q->where(function ($query) {
        $query->where('gender', 'Male')
            ->where('age', '>=', 18);
    })->orWhere(function($query) {
        $query->where('gender', 'Female')
            ->where('age', '>=', 65); 
    })

20、orWhere with multiple parameters

    $q->orWhere(['b' => 2, 'c' => 3]);