Get ids array from related laravel model which is having belongsToMany relationship

Question

I have a model Role which belongs to many Users.

Class Role {
     public $fillable = ["name"];

     public function users()
     {
          return $this->belongsToMany('App/Models/User')->select(['user_id']);
     }
}

When I retrieve users using with query in Role. I want It would return only user_ids array

 Role::with("users")->get();

it should return the following output

 [ 
   {
     "name": "Role1",
     "users" : [1,2,3]
   },
   {
     "name": "Role2",
     "users" : [1,2,3]
   }
 ]

Currently it gives following output

[ 
   {
     "name": "Role1",
     "users" : [
        {
           user_id : 1
        },
        {
           user_id : 2
        },

        {
           user_id : 3
        }
   },
   {
     "name": "Role2",
     "users" : [
        {
           user_id : 1
        },
        {
           user_id : 2
        },

        {
           user_id : 3
        }
     ]
   }
 ]

Solution

Personally, I wouldn't change the users() relationship, but maybe add an accessor for user IDs

class Role {
    protected $fillable = ["name"];

    // adding the appends value will call the accessor in the JSON response
    protected $appends = ['user_ids'];

    public function users()
    {
         return $this->belongsToMany('App/Models/User');
    }

    public function getUserIdsAttribute()
    {
        return $this->users->pluck('user_id');
    }
}

Then you still have a working relationship, but can access the user IDs as an array in the Role response. If that doesn't work for you, as mentioned by @Creator, you could probably just add ->pluck('id') in the relationship rather than the select()

Comments

[llioor]

In Laravel 5.5+ I needed to do return $this->users->pluck('pivot.user_id'); or just to use the "id".

[AndrewMcLagan]

THIS IS SLOW - you are accessing this using $this->users->pluck() should be $this->users()->pluck('feild')->get()

[benJ]

@AndrewMcLagan erm, nope, calling $this->users() returns the query builder. Calling $this->users returns the eager-loaded collection. You could do $this->users()->pluck('field'), but that would be slower as you're repeating the query.

[giovannipds]

here the guys used $this->users()->allRelatedIds();. Does your tip apply here too, @benJ?

[giovannipds]

Tested both and they make different queries for me: 1) pluck seems to make this long query: select agents.*, agent_price_table.price_table_id as pivot_price_table_id, agent_price_table.agent_id as pivot_agent_id from agents inner join agent_price_table on agents.id = agent_price_table.agent_id where agent_price_table.price_table_id = 20; 2) while allRelatedIds makes a very shorten one: select agent_id from agent_price_table where price_table_id = 20. But apparently both make an additional query.

[giovannipds]

@benJ I tried it here and apparently either way will going to make a query for each row.

[CodeToLife]

just a comment. Then you will cal it as $aRole->getUserIdsAttribute() not $aRole->getUserIdsAttribute