This is not very DRY since the knowledge that comments have a `comments` attribute is repeated both here and in the params method. We could better do this in one of two ways:

```
@comment = @article.comments.new(comment_params)
@comment.user = current_user
```

```
@comment = @article.comments.new(comment_params.merge(user: current_user))
```

`merge` is an instance method of hashes that merges in the keys/values from another hash.