How can I count nested relationships using Laravel's withCount and hasManyThrough?

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I'm building an application with Laravel, InertiaJS, and Vue3.
There are three main tables: Operators, Locations, and Terminals. Terminals belong to Locations and Locations belong to Operators, with no direct relation between Operators and Terminals.

I want to display a list of Operators with a count of their locations and the total number of terminals across those locations.

For example, if Operator John Doe has 3 locations and each location has 3 terminals, the output should be:

John Doe | 3 | 9

I initially tried something like this:

PHP
$operators = Operator::countWith('locations')->countWith('locations.terminals')->get()

This approach doesn't work. Is there an alternative way to achieve these counts using Laravel's Eloquent relationships?

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

You can achieve this by defining an intermediate relation between Operators and Terminals using Laravel’s built-in support for "hasManyThrough". This lets you count Terminals directly from the Operator model.

Step 1: Define Relationships

In your Operator model, define the following relationships:

PHP
class Operator extends Model
{
    // Operator has many Locations
    public function locations()
    {
        return $this->hasMany(Location::class);
    }

    // Operator has many Terminals through Locations
    public function terminals()
    {
        return $this->hasManyThrough(Terminal::class, Location::class);
    }
}

Step 2: Retrieve the Operators with Counts

Now, you can use Laravel's withCount() to get the counts of both locations and terminals:

PHP
$operators = Operator::withCount(['locations', 'terminals'])->get();

Each Operator instance will now have locations_count and terminals_count fields available. For example, if "John Doe" has 3 locations and each location has 3 terminals, you'll see:

John Doe | 3 | 9

Alternative Approach

If you choose not to use hasManyThrough, you could use separate subqueries. However, the hasManyThrough approach is cleaner and more maintainable for this common scenario.

Summary

By defining a terminals relation in the Operator model using hasManyThrough, you can easily leverage withCount() to get the desired counts in a single query. This approach keeps your code clean and fully utilizes Laravel's Eloquent ORM features.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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Answer by EclipseHunter811 • 1 month ago

I find solution in Laravel documentation eloquent relationships hasManyThrough

In Operator Model I create terminals method

PHP
public function terminals(): HasManyThrough {
        return $this->hasManyThrough(Terminal::class, Location::class);
    }

and in OperatorController index method

PHP
public function index() {
    $operators = Operator::withCount('locations')->withCount('terminals')->get();
    return Inertia::render('Operator/Index', [
        'operators' => OperatorResource::collection($operators)
    ]);
}

In OperatorResource toArray method

PHP
public function toArray(Request $request): array {
    return [
        'id' => $this->id,
        'name' => $this->name,
        'locations_count' => $this->locations->count(),
        'terminals_count' => $this->terminals->count(),
    ];
}

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Discussion

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How can I count nested relationships using Laravel's withCount and hasManyThrough?

2 Answers

Step 1: Define Relationships

Step 2: Retrieve the Operators with Counts

Alternative Approach

Summary

Discussion

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