提交表单时从模型创建新对象

I have this template to create a new instance of my Poll model

{{ Form::model(new Poll, array('route' => 'create')) }}
    {{ Form::label('topic', 'Topic:') }}
    {{ Form::text('topic') }}

    {{ Form::submit() }}
{{ Form::close() }}

This is the model

//models/Polls.php
class Poll extends Eloquent {}

This is the migration

//database/migrations/2014_03_16_182035_create_polls_table
class CreatePollsTable extends Migration {

    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up() {
        Schema::create('polls', function(Blueprint $table) {
            $table->increments('id');
            $table->timestamps();
            $table->string('topic');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down() {
        Schema::drop('polls');
    }

}

What steps do I need to do know to build my object in the controller?

This is what I have, but when I post the form, it returns a 500 Status Code

//controllers/poll.php
class Poll extends BaseController {

    public function index() {
        return View::make('home');
    }

    public function create() {
        $topic = Input::get('topic');

        // if ($topic === "")
        //  return View::make('home');

        $poll = Poll::create(array('topic' => $topic));
        var_dump($poll);

        return View::make('poll', array('poll' => $poll));
    }

First of all you don't need to use model binding when you are creating a new model but only when you are trying to load an existing model from database for editing so the Form should be something like this:

@if(isset($poll))
{{ Form::model($poll, array('route' => 'update', $poll->id)) }}
@else
{{ Form::open(array('route' => 'create')) }}
@endif
    {{ Form::label('topic', 'Topic:') }}
    {{ $errors->first('topic') }}
    {{ Form::text('topic') }}
    {{ Form::submit() }}
{{ Form::close() }}

In your controller, for creating a new model when using create method, try it like this:

public function create() {
    $topic = Input::get('topic');
    $rules = array('topic' => 'required');
    $validator = Validator::make($topic, $rules);
    if($validator->fails()) {
        return Redirect::back()->withInput()->withErrors();
    }
    else {
        Poll::create(array('topic' => $topic));
        return Redirect::action('Poll@index');
    }
}

Index method:

public function index()
{
    $polls = Poll::all();
    return View::make('home')->with('polls', $polls);
}

When you need to load an existing Topic to edit, you may load it from database and pass it to the form using something like this (In Poll class):

public function edit($id)
{
    $poll = Poll::get($id);
    return View::make('poll', array('poll' => $poll));
}

The update method in the Poll class:

public function update($id)
{
    // Update the Poll where id = $id
    // Redirect to Poll@index 
}

Declare the routes using proper methods (Use Route::post(...) for create and Update). Read more on documentation and specially the Route::model() and also about Mass Assignment.