title: Form Model Binding with relationship
body: <blockquote>
    <p>I already looked at this post but I can't seem to make it right:</p>
    
    <p><a href="https://stackoverflow.com/questions/16873638/laravel-form-model-binding">Laravel form model binding</a></p>
    
    <p>I get this error:</p>
    
    <p><a href="https://gyazo.com/2ea7b7bb6a19d588829447ee1a92053e" rel="nofollow noreferrer">https://gyazo.com/2ea7b7bb6a19d588829447ee1a92053e</a>   I use laravel 5.2
    for this.</p>
    
    <p>some screenshots:</p>
    
    <p><a href="https://gyazo.com/1b2c35e660dfe1aae69a02703733d083" rel="nofollow noreferrer">https://gyazo.com/1b2c35e660dfe1aae69a02703733d083</a>
    <a href="https://gyazo.com/3d6f294473f6e54650a4a4403dc2777e" rel="nofollow noreferrer">https://gyazo.com/3d6f294473f6e54650a4a4403dc2777e</a>
    <a href="https://gyazo.com/a59aebc7362f51f9ac27852ea032f962" rel="nofollow noreferrer">https://gyazo.com/a59aebc7362f51f9ac27852ea032f962</a></p>
  </blockquote>