Trait to work with Silber Bouncer to add some role assignment helpers.

AssignsRoles.php

<?php

namespace App;

use Illuminate\Support\Str;
use Silber\Bouncer\Database\Role;

/**
 * Trait AssignsRoles.
 * Works with Silber\Bouncer to add some role assignment helpers
 */
trait AssignsRoles
{
    /**
     * Get a list of assignable roles
     *
     * @return mixed
     */
    public function assignableRoles()
    {
        $roles = Role::all();
        $abilities = $this->getAbilities()->lists('name')->all();

        return $roles->reject(function($role) use ($abilities) {
            if (! in_array($this->buildRoleAssignmentAbility($role->name), $abilities)) {
                return true;
            };
        });
    }

    /**
     * Check if a user can assign a role.
     * @param $role \Silber\Bouncer\Database\Role|string|integer
     *
     * @return boolean
     */
    public function canAssignRole($role)
    {
        $role = $this->getRoleName($role);

        return $this->can($this->buildRoleAssignmentAbility($role));
    }

    /**
     * Determine role title
     * @param $role \Silber\Bouncer\Database\Role|string|integer
     *
     * @return string
     * @throws \RuntimeException
     */
    protected function getRoleName($role)
    {
        if (is_string($role)) {
            return $role;
        }

        if (is_integer($role)) {
            return Role::find($role)->name;
        }

        if ($role instanceof Role) {
            return $role->name;
        }

        throw new \RuntimeException('Unable to identify role.');
    }

    /**
     * Remove all roles from this user.
     */
    public function retractAll()
    {
        $this->roles()->detach();
    }

    /**
     * Build the assignment ability string, used when checking abilities.
     *
     * @param $title string
     *
     * @return string
     */
    protected function buildRoleAssignmentAbility($name)
    {
        return 'assign-' . Str::slug($name) . '-role';
    }
}