laravel multi-level many to many

Question

I have 3 models, Industry, Category, Machine and they are linked as following

• Industry can have multiple Categories, and a Category can be in only one Industry (industry Id stored in category table)
• A category can have multiple machines, and a machine can be in multiple Categories (using pivot table)

Problem : I want to show all machines in an industry, how i can do that?

What I did so far : I retrieved all category ids related to a specific industry like : $industry->categories()->pluck("id"). I don't know what I can do next to get all machines

Answer 1

Industry model relation:

class Industry {
    public function categories(){
        return $this->hasMany(Category::class);
    }
}

Category model relation:

class Category {
    public function indusry(){
        return $this->hasOne(Industry::class);
    }

    public function machines(){
        return $this->belongsToMany(Machine::class);
    }
}

Machine model relation:

class Machine {
    public function categories(){
        return $this->belongsToMany(Category::class);
    }
}

you can use whereHas method like this:

$machines = Machine::whereHas('categories', function($query) {
    $query->whereHas('indusry', function($sub_query) {
        $sub_query->where('name', {your_industry});
    });
});