Laravel 5.2 Undefined variable theme - php

Question

I'm making a forum and the if the user clicks on a theme, he gets redirected to the page where all the topics are that belong to that theme. What I'm trying to do, is that the user is able to click on the topic and gets redirected to it.
The problem is, is that I get an error saying Undefined variable: theme
As you can see in the code below, I have a foreach loop in my theme.blade.php which loops all the topics that belong to the theme he/she clicked on. In the beginning of the loop there is a <a href="{{ route('showtopic', ['theme_id' => $theme->id, 'topic_id' => $topic->id]) }}"1 which is supposed to bring the user to the topic that he/she clicked on. The URL that is supposed to show is forum.dev/theme/{theme_id}/topics/{topic_id} But that doesn't work.
And it gives me that error code. All the code is below, If i miss some code, Please inform me about it and i'll update the question. Thanks in advance
theme.blade.php
<div class="col s12">
<div class="card">
<div class="card-content"><span class="card-title"> - Topics</span>
<div class="collection">
#foreach($topics as $topic)
<a href="{{ route('showtopic', ['theme_id' => $theme->id, 'topic_id' => $topic->id]) }}" class="collection-item avatar collection-link"><img src="/uploads/avatars/{{ $topic->user->avatar }}" alt="" class="circle">
<div class="row">
<div class="col s6">
<div class="row last-row">
<div class="col s12"><span class="title">Theme - {{ $topic->topic_title }}</span>
<p>{!! str_limit($topic->topic_text, $limit = 125, $end = '...') !!}</p>
</div>
</div>
<div class="row last-row">
<div class="col s12 post-timestamp">Posted by: {{ $topic->user->username }} op: {{ $topic->created_at }}</div>
</div>
</div>
<div class="col s2">
<h6 class="title center-align">Replies</h6>
<p class="center replies">{{ $topic->replies->count() }}</p>
</div>
<div class="col s2">
<h6 class="title center-align">Status</h6>
<div class="status-wrapper center-align"><span class="status-badge status-open">open</span></div>
</div>
<div class="col s2">
<h6 class="title center-align">Last reply</h6>
<p class="center-align"></p>
<p class="center-align">Tijd</p>
</div>
</div>
</a>
#endforeach
</div>
</div>
</div>
</div>
Web.php
Route::get('/', 'ThemesController#index')->name('home');
Route::get('/theme/{theme_id}/topics', 'ThemesController#show')->name('showtheme');
Route::get('/theme/{theme_id}/topics/{topic_id}', 'TopicsController#topic')->name('showtopic');
Route::group(['middleware' => 'App\Http\Middleware\AdminMiddleware'], function() {
//THEMES
Route::get('/theme/{theme_id}/edit', 'ThemesController#edit')->name('edittheme');
Route::patch('/theme/{theme_id}/edit', 'ThemesController#update')->name('updatetheme');
Route::get('/theme/create', 'ThemesController#create')->name('createtheme');
Route::post('/theme/create', 'ThemesController#save')->name('savetheme');
Route::delete('/theme/{theme_id}/delete', 'ThemesController#destroy')->name('deletetheme');
//TOPICS
Route::get('/theme/{theme_id}/topics/{topic_id}/edit', 'TopicsController#edit')->name('edittopic');
Route::patch('/theme/{theme_id}/topics/{topic_id}/edit', 'TopicsController#update')->name('updatetopic');
Route::get('/theme/{theme_id}/topics/create', 'TopicsController#create')->name('createtopic');
Route::post('/theme/{theme_id}/topics/create', 'TopicsController#save')->name('savetopic');
Route::delete('/theme/{theme_id}/topics/{topic_id}/delete', 'TopicsController#destroy')->name('deletetopic');
});
Route::get('user/profile', 'UserController#profile')->name('showprofile');
Route::post('user/profile', 'UserController#update_avatar');
TopicsController.php (Show method)
public function show($id)
{
$theme = Theme::find($id);
$topics = Topic::find($id);
return view('topics/topic')->with('topics', $topics)->with('theme', $theme);
}

Answer 1

I don't know if you can use the double '->with' option.
What will work is the following:
return view('topics/topic', ['topics' => $topics, 'theme'=> $theme]);
You pass an array as the second argument of the view. You can add as many keys and variables as you like.