Basic role implementation for Laravel 5

HasRoles.php

<?php

namespace App\Traits;

use Illuminate\Support\Str;
use App\Role;

/**
 * Adds roles to a model
 * Note: requires a Role model pivot table {model}_roles and a role table with
 * the columns [id, key, name]
 *
 * @param array $roles
 */
trait HasRoles
{
    /**
     * Filter based on role.
     *
     * @param string|array $roles
     *
     * @return \Illuminate\Database\Eloquent\Builder
     */
    public function scopeRole($query, $roles)
    {
        foreach ((array) $roles as $role) {
            $query = $query->whereHas('roles', function ($query) use ($role) {
                $query->where('key', $role);
            });
        }

        return $query;
    }

    /**
     * Returns all roles.
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsToMany
     */
    public function roles()
    {
        return $this->belongsToMany(
                'App\Role',
                Str::snake(class_basename($this)).'_role'
            )->withTimestamps();
    }

    /**
     * Return array of roles.
     *
     * @return array
     */
    public function getRoleKeys()
    {
        return array_pluck($this->roles->toArray(), 'key');
    }

    /**
     * Returns true if model matches passed role(s).
     *
     * @param string|array $roles
     *
     * @return bool
     */
    public function hasRole($roles)
    {
        $diff = array_diff(
            (array) $roles,
            $this->getRoleKeys()
        );

        // True only if model has ALL requested roles
        return (count($diff) === 0);
    }

    /**
     * Iterates over the roles that match the passed array and passes each role
     * to the passed $callback closure.
     *
     * @param string|array $roles    Name or list of role keys.
     * @param \Closure     $callback Closure to call on each matching role.
     *
     * @return Illuminate\Database\Eloquent\Model
     */
    private function roleIterator($roles, $callback)
    {
        $roles = Role::whereIn('key', (array) $roles)->get();
        foreach ($roles as $role) {
            $callback($role);
        }
        $this->load('roles');

        return $this;
    }

    /**
     * Add role(s) to model.
     *
     * @param string|array $roles Name or list of role keys.
     *
     * @return Illuminate\Database\Eloquent\Model
     */
    public function addRole($roles)
    {
        return $this->roleIterator($roles, function ($role) {
            $this->roles()->attach($role->id);
        });
    }

    /**
     * Remove role(s) from model.
     *
     * @param string|array $roles Name or list of role keys.
     *
     * @return Illuminate\Database\Eloquent\Model
     */
    public function removeRole($roles)
    {
        return $this->roleIterator($roles, function ($role) {
            $this->roles()->detach($role->id);
        });
    }
}