Laravel get value from my function in Model - php

Question

My model Dispatch has a field invoice_id.
It is a foreign key so i can get the invoice details using the below code:
protected $fillable = [
'id',
'truck_no',
'driver_name',
'driver_phone',
'gps_details',
'invoice_id',
];
public function invoice(){
return $this->belongsTo('App\Invoice')->select('id','invoice_no','permit_id');
}
Now I want to get the value permit_id from invoice() so i can use it to get the details of the Permit.
permit_id = id of Permit model
So I use the below code to get the permit data.
public function permit(){
return $this->hasOne('App\Permit','id',$this->invoice()->permit_id);
}
Update:
My Invoice Model has :
class Invoice extends Model
{
protected $fillable = [
'id',
'invoice_no',
'invoice_date',
'permit_id',
];
public function permit(){
return $this->hasOne('App\Permit', 'id', 'permit_id');
}
}
My Permit Model has:
class Permit extends Model
{
protected $fillable = [
'permit_type',
'permit_no',
'application_no',
'supply_unit',
'supply_unit_id' ,
];
public function supplyunit(){
return $this->hasOne('App\SupplyUnit','id','supply_unit_id');
}
}
And as per suggestions i have added below code in my Dispatch Model:
class Dispatch extends Model
{
protected $fillable = [
'id',
'truck_no',
'driver_name',
'driver_phone',
'gps_details',
'invoice_id',
];
public function invoice(){
return $this->hasOne('App\Invoice','id','invoice_id');
}
public function permit(){
return $this->hasOne('App\Permit','id','permit_id');
}
}
But it doesn't work. What should i do to achieve the above? Is there any other solutions please suggest.

Answer 1

Assuming each invoice has one permit, your relationship definition should look like this:
public function permit(){
return $this->hasOne('App\Permit', 'id', 'permit_id');
}
Edit: If invoice belongs to permit, which is the inverse, your relationship would look like this instead:
public function permit(){
return $this->belongsTo('App\Permit', 'permit_id');
}
Edit: Based on your updated question, I think you got the relationship definitions a bit wrong. The following should work:
Since you have an invoice_id column in App\Dispatch, it means that each App\Dispatch belongs to an invoice.
In App\Dispatch, your relationship definition should be as follows:
public function invoice() {
return $this->belongsTo('App\Invoice');
}
// permit does not belong to `App\Dispatch` as a direct relationship
// it should be removed
In App\Invoice, your relationship definition should be as follows:
public function dispatch() {
return $this->hasOne('App\Dispatch');
}
public function permit() {
return $this->belongsTo('App\Permit');
}
In App\Permit, your relationship definition should be as follows:
public function invoice() {
return $this->hasOne('App\Invoice');
}
To then retrieve the permit id from an Invoice model, you would do
$invoice->permit->id;

Answer 2

Change this line
return $this->belongsTo('App\Invoice')->select('id','invoice_no','permit_id');
To
return $this->belongsTo('App\Invoice');
And add the following code on Invoice
public function permit(){
return $this->belongsTo('App\Permit');
}
And you can access as
Dispatch::find($id)->invoice->permit->id;
Or if you want all the information
Dispatch::find($id)->invoice->permit;