Laravel 5.5 Relationships - laravel

Question

I'm trying to implement relationships between models and i recieve "Trying to get property 'products' of non-object" and i don't understand why, because i used this before in the same way and it's worked fine.
The logic of relationship is that 1 Merchant hasMany Products
this is the code that i'm using:
Merchant Model:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Merchant extends Model {
protected $table = "merchants";
protected $fillable = [
'merchant_id', 'merchant_name', 'secret_key', 'merchant_address', 'merchant_phone', 'merchant_admin',
'merchant_contact', 'merchant_mail', 'merchant_description', 'enable', 'created_at', 'updated_at'];
public function users() {
//many to many
return $this->belongsToMany('App\User');
}
public function branchOffices() {
return $this->hasMany('App\BranchOffice', 'merchant_id', 'merchant_id');
}
public function products() {
return $this->hasMany('App\Products', 'merchant_id', 'merchant_id');
}
public function transactions() {
return $this->hasMany('App\Transaction', 'merchant_id', 'merchant_id');
}
public function readers() {
return $this->hasMany('App\Reader', 'merchant_id', 'merchant_id');
}
}
Product Model:
<?php
namespace App;
use Illuminate\Database\Eloquent\Model;
class Product extends Model {
protected $table = "products";
protected $fillable = [
'id', 'barcode', 'description', 'price', 'currency_id', 'merchant_id', 'branch_id',
'enable', 'created_at', 'updated_at'];
public function merchants() {
return $this->belongsTo('App\Merchant', 'merchant_id', 'merchant_id');
}
public function currencies() {
return $this->belongsTo('App\Currency', 'iso_4712', 'currency_id');
}
public function branch_sectors() {
return $this->belongsToMany('App\BranchSector');
}
}
And this is the method in ProductController:
public function merchantProducts() {
$products = Merchant::find('merchant_id')->products;
return $products;
}
If someone can help me i'll be very thankfull.
Thanks in advance!!

Answer 1

Assume merchant is not guaranteed existing in database giving merchant id, it is better off to check if merchant exists, and retrieves its products if so.
$products = collect();
$merchant = Merchant::find($merchant_id);
if($merchant) {
$products = $merchant->products;
}
return $products;

Answer 2

all!!
Finally i solved this problem using resources in this way:
public function merchantProducts(Request $request) {
$merchant_id = $request->merchant_id;
$products = Product::where('merchant_id', $merchant_id)->paginate(15);
return ProductResource::collection($products);
}
Thanks to all!!