how to generate error message in laravel - laravel

Question

Hello stackoverflow geeks, I'm in my final stages of the laravel learning curve all thanks to you guys.
However, i need to generate a warning message like "You cannot delete a role assigned to a user" every time a user tries to delete a role assigned to a user.
instead it loads a page with an sql error. how to i do it?
And how do i avoid a password that has been already been stored from being hashed again. eg:- $2y$10$p8JwI5P4yE2UFo2.vHP99.0dP2jU7ll/9w73IzUa9/yegKOSTHJWq is always hashed every time i edit a user's information.
Thanks you all who've made learning laravel easy for me by answering in time
code
public function destroy(Request $request,$id)
{
// delete
// $role = Role::find($id);
//$role->delete();
$role = Role::find ($id);
if ($role->users() !=null) {
return redirect()->back()->withInput(['warning' => 'Not allowed']);
}
$role->delete();
// redirect
Session::flash('message', 'Record successfully deleted!');
Session::flash('alert-type', 'success');
return Redirect::to('role');
}

Answer 1

This highly depends on how you want to handle the errors. You can either catch the sql exception and display your custom error OR what is probably better for you is to handle the incoming request, validate it and return an error if validation fails.
Here are the validation docs : https://laravel.com/docs/5.3/validation
You have multiple options on how to validate a request. Simple example to validate a title is unique in the table posts and is maximum 255 chars long:
$this->validate($request, [
'title' => 'required|unique:posts|max:255'
]);
If you cannot find a rule that is helping you simply define your own validation rule https://laravel.com/docs/5.3/validation#custom-validation-rules
Ofcourse you can also do the validation manually. In your request or in your controller (depends on your setup) just check for it
// assuming you want to delete an entry
public function delete(Request $request, $id)
{
$role = App\Role::findOrFail($id);
if ($role->users() != null) {
return redirect()->back()->withInput(['message' => 'Not allowed']);
// now you can output $message
}
$role->delete();
return ...
}