Call to undefined method Illuminate\Database\Query\Builder in laravel

I have 2 models set up and they both need a relationship setup so they can interact with each other etc like any other relationship method. I have the files set up like so:

PostImage.php model:

<?php

class PostImage extends Eloquent {
    protected $guarded = array();

    public static $rules = array();

    public function post(){
        return $this->belongsTo('Post');
    }

    public function __construct(array $attributes = array()) {
    // Profile pictures have an attached file (we'll call it photo).
    $this->hasAttachedFile('image', [
        'styles' => [
            'thumbnail' => '100x100#'
        ]
    ]);

    parent::__construct($attributes);
    }

}

Post.php model:

<?php

class Post extends Eloquent {
    use Codesleeve\Stapler\Stapler;
    protected $guarded = array();

    public static $rules = array(
        'title' => 'required',
        'body' => 'required'
    );

    public function postImages()
    {
        return $this->hasMany('PostImage');
    }

    public function __construct(array $attributes = array()) {
    $this->hasAttachedFile('picture', [
        'styles' => [
            'thumbnail' => '100x100',
            'large' => '300x300'
        ],
        // 'url' => '/system/:attachment/:id_partition/:style/:filename',
        'default_url' => '/:attachment/:style/missing.jpg'
    ]);

    parent::__construct($attributes);
    }

}

PostsController.php store function:

/**
     * Store a newly created resource in storage.
     *
     * @return Response
     */
    public function store()
    {
        $post = new Post(Input::get());
        $post = Post::create(['picture' => Input::file('picture')]);
        $post->save();

        foreach(Input::file('images') as $image)
        {
            $postImage = new PostImage();             // (1)
            $postImage->image = $image;                    // (2)
            $post->postImages()->save($postImage);    // (3)
        }

        return Redirect::route('posts.create')
            ->withInput()
            ->withErrors($validation)
            ->with('message', 'There were validation errors.');
    }

In my view for the create I have a form that basically asks for the images like so:

{{ Form::open(array('route' => 'posts.store', 'files' => true)) }}
    <ul>
        <li>
            {{ Form::label('title', 'Title:') }}
            {{ Form::text('title') }}
        </li>

        <li>
            {{ Form::label('body', 'Body:') }}
            {{ Form::textarea('body') }}
        </li>

        <li>
            {{ Form::file('picture') }}
        </li>
        <li>
            {{ Form::file( 'images[]', ['multiple' => true] ) }}
        </li>

        <li>
            {{ Form::submit('Submit', array('class' => 'btn btn-info')) }}

    </ul>
{{ Form::close() }}

When it comes to submitting the form to create the post I get this error below:

Call to undefined method Illuminate\Database\Query\Builder::hasAttachedFile()

Can anyone tell me why this would give that error and what I am doing to create this error at all?

Thanks,