Laravel 5中的子关系？

Question

Currently I've got 3 models, Listing, Offer & Payment which have the following relationships:

Listing

class Listing extends Model {

    public function offers() {
        return $this->hasMany(\App\Models\Offer::class)->orderBy('created_at', 'desc');
    }

}

Offer

class Offer extends Model {

    public function payment() {
        return $this->hasOne(\App\Models\Payment::class, 'item_id', 'id')->where('item_type', \App\Models\Offer::class)->where('status', '1');
    }

    public function listing() {
        return $this->belongsTo(\App\Models\Listing::class)->withTrashed();
    }

}

Payment

class Payment extends Model {

    public function offer() {
        return $this->belongsTo(\App\Models\Offer::class, 'item_id', 'id')->withTrashed();
    }

}

How can I go from them Listing model & return a relationship with the payments table directly?

Listing can have unlimited amounts of Offer but Offer can only have 1 max Payment

To find any corresponding payment information, I'm having to query the Offer based on the listing_id within the model, and then access the Offer->payment, when I'd much prefer to be able to just do something like this:

$transaction_id = $id;

$listing = Listing::whereHas('payment', function($q) use ($id) {
        $q->where('transaction_id', $id);
        $q->where('user_id', Auth::user()->id);
})->first();

Answer 1

Use HasManyThrough:

public function payments() {
    return $this->hasManyThrough(Payment::class, Offer::class, null, 'item_id')
        ->where('payments.item_type', Offer::class)
        ->where('payments.status', '1')
        ->orderBy('offers.created_at', 'desc');
}