What is the Laravel way to check if the POST Request has a field left empty?

Question

The requirement was to update user roles. The role can be empty(left blank), one, or more than one as provided in the form field roles[].

Here is the view form:

@foreach ($roles as $role)
  <div class="checkbox">
     <label><input name="roles[]" type="checkbox" value="{{$role->id}}" {{ $user->roles->contains($role->id) ? 'checked' : '' }}>{{$role->name}}</label>
  </div>
@endforeach

The condition inside UserController::update() is:

if ($request->roles) {
    // update user roles
}

Everything works fine except for one case. Sometimes the user has to stay without any role.

if($request->roles), isset($request->roles), and !empty($request->roles) .. are all giving the same old fashioned reply(null, '', true/flase).

Case: when there is one or more role(s) assigned:

  +request: ParameterBag {#41 ▼
    #parameters: array:6 [▼
      "_method" => "PUT"
      "_token" => "a8oIPQFBMbhjanikX8v83qeOcfRE0N4UKTcTQDig"
      "name" => "New User Name"
      "email" => "[email protected]"
      "password" => ""
      "roles" => array:2 [▼
        0 => "2"
        1 => "3"
      ]
    ]
  }

Case: when there no role assigned OR need to remove(detach) the previously assigned role:

  +request: ParameterBag {#41 ▼
    #parameters: array:5 [▼
      "_method" => "PUT"
      "_token" => "a8oIPQFBMbhjanikX8v83qeOcfRE0N4UKTcTQDig"
      "name" => "New User Name"
      "email" => "[email protected]"
      "password" => ""
    ]
  }

So the question (requirement) is:

How to differentiate when the field value of an HTML Post form has been submitted as empty(unchecked here) or if there was no such a field in the view form? Is there an eloquent* way in Laravel to find/list the form fileds from the Request object?

[PS: Trying another hidden field or do some frontend jQuery will not be appreciated]

Answer 1

You will need to identify this problem in the design of your application.

How to differentiate when the field value of an HTML Post form has been submitted as empty(unchecked here) or if there was no such a field in the view form? Is there an eloquent* way in Laravel to find/list the form fileds from the Request object?

When does that form should not have a roles[] field? You should have a marker that will tell your application that this form doesn't have a roles[] field.

Something like, when this form is used when an ordinary user is updating his/her profile, he/she will not be able to update his/her roles.

Because your problem is indeed the default behavior of forms, as answered in this question: Submit an HTML form with empty checkboxes

So there will be a different process for forms which DO NOT HAVE have a roles field and different process for forms which DO HAVE a roles field.

To add to your implementation, you can retrieve the roles field like this:

$roles = $request->input('roles', []);

After which you can just use sync to the relationship method of your model.

$user->roles()->sync($roles);