---
title: Disambiguate Rails helpers
teaser:
tags: web,rails
author: Eric Torrey
published_on: 2007-07-24
---

Here at thoughtbot we strive to make explicit, agile code.  We know the
specification changes, it's what we're machined for.  The place that changes the
most, and is usually the hardest to maintain are the views.  As my colleague
pointed out the views usually [run wild], so we use helper methods to prevent a
long method chain, and keep things a little more readable.  Sometimes however
that usually leads to methods that aren't used, or methods that are duplicated.

[run wild]: https://thoughtbot.com/blog/views-gone-wild

For example.  Let's assume you have a Blog, that belongs to a User, and has many
Posts.  Pretty standard right?  There is no requirement for the Blog to have
it's own title so instead we use a helper method.  On `blogs#show` we use a Blog
helper method defined here:

```ruby
module BlogsHelper

  def display_title_for(blog)
    "#{blog.user.name} - The Blog!"
  end

end
```

Good, now when a user clicks on a Post for that Blog, we get to `posts#show`.
At the top of the page, we want to display the title of the Blog.  So we try to
call `#display_title_for` and get a `NameError`, something along the lines of
`undefined local variable or method.`

We can't use the method in the BlogsHelper from the Post's views yet.  We could
go into the Post's controller and add this:

```ruby
class PostsController < ApplicationController

  helper :blogs

  def show
    @post = Post.find params[:id]
  end

end
```

I don't like this solution, sure your being <abbr title="Don't Repeat
Yourself">DRY</abbr>, but your not being explicit.  What happens when someone
wants to change the display of the Blog's title, and they are looking at the
`posts#show` view?  They will immediately look for a display_title_for(blog) in
the Post's helper - too bad it's not there.

Another solution would be to duplicate the method on the PostsHelper.  Although
this also is a poor solution, if someone wants to change the way the blog title
is being displayed, it will need to be changed in two spots.

So, I want helpers to be called explicitly, and defined explicitly.  I want to
know what is being called, and where it's being called from.  Let's redefine the
`display_title_for(blog)` on the `BlogsHelper`:

```ruby
module BlogsHelper

  def self.display_title_for(blog)
    "#{blog.user.name} - The Blog!"
  end

end
```

Now that we have defined it as a module method we can use it in the post#show
view like so.

```ruby
BlogsHelper.display_title_for(@post.blog)
```

Now we have explicit, dry, maintainable code.