Получить все CadModels, где Category id = ‘id’ ….. Laravel 5.4

Я пытаюсь получить все CadModels, где category_id = $ category_id из таблицы cadmodel … Я не знаю, где я ошибаюсь … Я получаю эту ошибку.

Указан неверный аргумент для foreach () (Просмотр:
C: \ Ampps \ WWW \ GCF \ ресурсы \ вид \ cadmodels \ index.blade.php)

Вот моя функция фильтра

public function filter(Categories $category_id)
{
$categories = Categories::all();
$cadmodels = CadModel::where('category_id', $category_id)->first();
return view('cadmodels.index',['cadmodels' => $cadmodels, 'categories' => $categories]);
}

Вот мой index.blade.php

@extends('layouts.app')

@section('content')
<div class="container">
<div class="row">
<div class="header-bottom-on">
<p class="wel">
<a href="">Welcome visitor you can login or create an account.</a>
</p>
<br>
<div class="header-can">
<ul class="social-in">
<li><a href="" target="_blank"><i class="facebook"> </i></a></li>
<li><a href="" target="_blank"><i class="twitter"> </i></a></li>
</ul>
<div class="search">
<form action="" method="post" id="searchBox" name="searchBox">
<input type="text" name="strSearch" value="Search" align="middle">
<input type="submit" value="" name="SubSearch2">
<center><a href="" style="font-size:x-small;">Advanced Search</a></center>
</form>
</div>
<div class="clearfix"> </div>
</div>
<div class="clearfix"></div>
</div>
<div class="col-md-3">
<h3 class="future">CATEGORIES</h3>
<div class="list-group">
<a href="" class="list-group-item">All Categories</a>
@foreach($categories as $category)
<a class="list-group-item" href="{{route('cadmodels.filter',$category->id)}}">{{$category->name}}</a>
@endforeach
</div>
</div>
<div class="col-md-9">
<div class="content-top-in">
<h3 class="future">FEATURED</h3>
@foreach($cadmodels as $cadmodel)
<a href="{{route('cadmodels.show',[$cadmodel->id])}}">
<div class="col-md-3 md-col" style="padding-bottom:20px;">
<div class="col-md">
<center><img src="{{ Storage::url($cadmodel->image_url) }}" border="0" alt="a"></center><br>
<div class="top-content">
<h5>{{ $cadmodel->name }}</h5>
<div class="white">
<p align="center" class="hvr-shutter-in-vertical hvr-shutter-in-vertical2 ">View</p>
<div class="clearfix"></div>
</div>
</div>
</div>
</div>
</a>
@endforeach
</div>
</div>
</div>
</div>
@endsection

CadModel Controller

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class CadModel extends Model
{
protected $fillable = ['name','category_id','description','image_url'];

}

Контроллер категорий

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Categories extends Model
{
protected $fillable = ['name'];

}