Laravel 5.0 hasManyThrough column not found issue - eloquent

Question

I am five days into Laravel and after hours of watching Jeffrey Way I decided to delve into building an app to learn.
I am stuck at the point of working with tables in a hasManyThrough layout and identifying the columns that are the linkage between the tables. Eloquent is trying to use a column called 'id" as primary key that it cannot find. In my tables I am using the naming convention tablename_id like below. In my class function, I nominate the columns to use, but it fails with the error:
QueryException in Connection.php line 620:
SQLSTATE[42S22]: Column not found: 1054 Unknown column 'cable_installations.id' in 'on clause' (SQL: select `cable_specifications`.*, `cable_installations`.`cable_specifications_id` from `cable_specifications` inner join `cable_installations` on `cable_installations`.`id` = `cable_specifications`.`cable_installations_id` where `cable_installations`.`cable_specifications_id` is null)
I am trying to retrieve:
A distinct list of cable specifications that are allowed with a selected cable_installation_method
Thanks!
TABLE 1: cable_specifications
cable_specifications_id (REPEATS)
other_columns...
TABLE 2: cable_installation_methods
cable_installation_methods_id (UNIQUE)
other_columns...
TABLE 3: cable_installations (PIVOT)
cable_specifications_id (REPEATS)
cable_installation_methods_id (REPEATS)
My classes are:
use Illuminate\Database\Eloquent\Model as Eloquent;
class CableInstallationMethod extends Eloquent {
protected $table = 'cable_installation_methods';
protected $fillable = [];
public function CableInstallation()
{
return $this->hasMany('CableInstallation');
}
public function CableSpecByInstall()
{
return $this->hasManyThrough('App\CableSpecification', 'App\CableInstallation', 'cable_specifications_id', 'cable_installations_id');
}
}
In my controller, I call this function per below:
public function VoltageDropLoad()
{
$InstallationMethods = CableInstallationMethod::all();
$CableSelected = CableInstallationMethod::where("cable_installation_methods_id", 1)->first();
$CableTypes = $CableSelected->CableSpecByInstall()distinct()->get()->toJson();
return view('pages.voltcalc', compact('InstallationMethods', 'CableTypes', 'CableTypes'));
}

Answer 1

Based on your CableInstallationMethod class, you may have missed defining the primary key field for your models:
use Illuminate\Database\Eloquent\Model as Eloquent;
class CableInstallationMethod extends Eloquent {
protected $table = 'cable_installation_methods';
/* Need to define $primaryKey column here, normally defaults to 'id' */
protected $primaryKey = 'cable_installation_methods_id';
protected $fillable = [];
public function CableInstallation()
{
return $this->hasMany('CableInstallation');
}
public function CableSpecByInstall()
{
return $this->hasManyThrough('App\CableSpecification', 'App\CableInstallation', 'cable_specifications_id', 'cable_installations_id');
}
}
With the primary key set you can also take advantage of using Model::find($id) instead of using Model:where(...)->first()
public function VoltageDropLoad()
{
$InstallationMethods = CableInstallationMethod::all();
$CableSelected = CableInstallationMethod::find(1);
$CableTypes = $CableSelected->CableSpecByInstall()->distinct()->get()->toJson();
return view('pages.voltcalc', compact('InstallationMethods', 'CableTypes', 'CableTypes'));
}