Can't get hasManyThrough to work - laravel

Question

I've got three tables:
nCompanies (model Company)
nTransactions (model Transaction)
nBrokers (model Broker)
One company may have many transactions
One broker may have many transactions
Company and Broker doesn't have a relation.
Now I would like to get a list of brokers for each company through the company transactions. In order to do this I thought hasManyThrough() would do the job. But I can't get it to work.
Within my company model I have this:
class Company extends Model
{
protected $table = 'nCompanies';
protected $primaryKey = 'nCompanyId';
public function transactions()
{
return $this->hasMany('App\Transaction', 'nCompanyId');
}
public function brokers()
{
//This does not work
return $this->hasManyThrough('App\Broker', 'App\Transaction', 'nCompanyId', 'nBrokerId');
}
}
The below works, but I would prefer to do this with in the model in order to get a collection of brokers for each company, company->brokers instead of a flat list.
$companies = DB::table('nCompanies')
->join('nTransactions', 'nCompanies.nCompanyId', '=', 'nTransactions.nCompanyId')
->join('nBrokers', 'nTransactions.nBrokerId', '=', 'nBrokers.nBrokerId')
->selectRaw('nBrokers.*, nCompanies.*)
->groupBy('nCompanies.nCompanyId', 'nBrokers.nBrokerId')
->get();
How could I solve this? Should I use something else instead of hasManyThrough?

Answer 1

I re-read your question, and realized you wanted to get the brokers and companies through transaction. I guess you already have both nCompanyId and nBrokerId in transactions table. Then I guess the brokers should be accessed in Transaction model then so you can have:
class Transaction extends Model
{
public function brokers()
{
return $this->hasMany('App\Broker', 'nBrokerId');
}
}
So you can call it with:
$brokers = Company::find(1)->transactions->where('id', '1')->brokers();
This is just an example of my thoughts about this though:
I don't know if this helps you get what you are trying to do. :)

Answer 2

HasManyThrough does not work here because the relationship between Transaction and Broker is wrong: While there is a HasMany relationship Company->Transaction, there only is a HasOne relationship Transaction->Broker. For HasManyThrough to work, both have to be HasMany though.
A proposed solution would be to use an accessor together with a subquery in your model, like this:
public function getBrokersAttribute()
{
$transactionIds = $this->transactions->groupBy('nBrokerId')->lists('nBrokerId');
return Broker::find($transactionIds);
}
Be aware that this would cause two seperate queries, even though Laravel would cache the result of $transactionIds after first load. Also, this solution does not support eager loading and is not recommended when working with many companies.
Alternatively, you could use some looping to keep the ability of eager loading:
public function getBrokersAttribute()
{
$brokers = new Collection();
foreach ($this->transactions as $transaction) {
if (!$brokers->contains($transaction->broker->nBrokerId)) {
$brokers->add($transaction->broker);
}
}
return $brokers;
}
With this example, you can eager load using ->with('transactions.broker').