Laravel Eloquent从多个相关表中获取数据

Question

i have a deliveryForecast model and i have to create an eloquent to get data from multiple table based on 2 columns.

this is my delivery_forecasts table

Schema::create('delivery_forecasts', function (Blueprint $table) {
        $table->increments('id');
        $table->enum('type',array('Quotation','Demo','Service Unit','Freebie','Back Job','Site Visit'));
        $table->string('type_id');
        $table->date('transaction_date');
        $table->time('transaction_time')->nullable();
        $table->enum('status',array('Pending','Approved','Cancelled'))->default('Pending');
        $table->boolean('queue')->default(0);
        $table->timestamps();
    });

the question is can i create the eloquent in model? or how to make condition?

for example:

class DeliveryForecast extends Model
{
    public function documents(){
        if(DeliveryForecast->type == 'Quotation'){
            return $this->belongsTo('App\Quotation','type_id','id');
        }
        if(DeliveryForecast->type == 'Demo'){
            return $this->belongsTo('App\Demo','type_id','id');
        }
        if(DeliveryForecast->type == 'Service Unit'){
            return $this->belongsTo('App\ServiceUnit','type_id','id');
        }
        and so on .....
    }
}

i don't have idea to create the condition to eloquent and my query should be like this:

$delivery_forecast = DeliveryForecast::with('documents')
        ->get();

any idea guys? thanks in advance.

Answer 1

As @Scopey said, take a look at polymorphic relations: https://laravel.com/docs/5.2/eloquent-relationships#polymorphic-relations

In order to implement polymorphic relationship You have to change Your migration to following:

    Schema::create('delivery_forecasts', function (Blueprint $table) {
        $table->increments('id');
        $table->morphs('type');
        $table->date('transaction_date');
        $table->time('transaction_time')->nullable();
        $table->enum('status', ['Pending', 'Approved', 'Cancelled'])->default('Pending');
        $table->boolean('queue')->default(0);
        $table->timestamps();
    });

and then change DeliveryForecast 's method to following:

public function document()
{
    return $this->morphTo('type');
}

And that's all. But I would strongly suggest to add relationship in Your Quotation , Demo and other models:

public function deliveryForecasts()
{
    return $this->morphMany('App\DeliveryForecast', 'type');
}

When querying $forecast->document Laravel will automatically fetch correct model for without any other conditional clauses.