UrlGenerationException: Missing required parameters for [Route: topics.update] [URI: topics/{topic}] - laravel

Question

I'm getting this error:
Missing required parameters for [Route: topics.update] [URI: topics/{topic}]. (View: C:\xampp\htdocs\phpboards\resources\views\topics\edit.blade.php)
This is link that will take user to edit:
Edit
This is the controller for edit:
$topic = Topic::find($id);
return view('topics.edit')->with('topic', $topic);
This is the Route:
Route::get('/boards/topics/edit/{id}', 'TopicController#edit');
This is the form for edit:
<div class="container">
{!! Form::open(['action' => 'TopicController#update', 'method' => 'POST']) !!}
<div class="form-group">
{{ Form::label('title', 'Title') }}
{{ Form::text('title', $topic->topic_title, ['class' => 'form-control', 'placeholder' => 'Title of the Post']) }}
</div>
<div class="form-group">
{{ Form::label('desc', 'Desc') }}
{{ Form::textarea('desc', $topic->topic_body, ['class' => 'form-control', 'placeholder' => 'Description of the Post']) }}
</div>
{{ Form::submit('Submit', ['class' => 'btn btn-default']) }}
{!! Form::close() !!}
</div>
What i have done wrong here??

Answer 1

Instead of:
{!! Form::open(['action' => 'TopicController#update', 'method' => 'POST']) !!}
use
{!! Form::open(['url' => route('topics.update', $topic->id), 'method' => 'POST']) !!}
because for your route you need to pass id of topic you want to update. Also it's more reasonable to use named routes instead Controller#method notation.

Answer 2

Let's admit your update() method is already implemented on your TopicController.
First you need to declare another route:
Route::put('/boards/topics/edit/{id}', 'TopicController#update');
// ^^^
then change your Form opening by this:
{!! Form::open(['action' => ['TopicController#update', $topic->id], 'method' => 'put']) !!}
// ^^^^^^^^^^ ^^^
it should works.