Laravel 5 - 没有为belongsTo显示任何关系

Its been a while since I have worked on a Laravel project and cannot see why this issue is happening.

I have a 'vehicles' table and also a 'customers' table.

In the vehicles table there is a row with a fields 'customer_id' that has the value of 1. There is a also a customer in 'customers' table with the id of 1.

In my Vehicle model I have:

public function customer()
{
    return $this->belongsTo('App\Customer');
}

But when returning the data from the query:

$vehicle = Vehicle::find($id);
dd($vehicle);

The relations array is blank.

Where my mistake on this one? No errors, just no data.

If you want to get a customer with the vehicle:

$vehicle = Vehicle::with('customer')->find($id);

https://laravel.com/docs/5.4/eloquent-relationships#eager-loading

Wouldn't it be better if you define you relations like, assuming this is a One-To-Many Relationship?

In the Vehicles Model:

public function customer()
{
    return $this->belongsTo('App\Customer', 'id', 'customer_id');
}

In the Customers Model

public function vehicle()
{
    return $this->hasOne('App\Vehicle', 'customer_id', 'id');
}

Then load whatever you need

$vehicle = Vehicle::find($id); 

But the relationship will be loaded only when called:

$vehicle->customer;