# GoogleAnalyticsMailer [![Build Status](https://secure.travis-ci.org/fabn/google_analytics_mailer.png)](http://travis-ci.org/fabn/google_analytics_mailer)

This gem automatically rewrites **absolute** links generated by ActionMailer. It intercepts all'`url_for` calls (so `link_to` calls are intercepted as well) and change the final url to add [Custom Campaign parameters](http://support.google.com/analytics/bin/answer.py?hl=en&answer=1033867) to your URLs.

## Installation

Add this line to your application's Gemfile:

    gem 'google_analytics_mailer'

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install google_analytics_mailer

## Usage

There are three level of customization for rewritten links:

 * **Class level:** Params specified at class level will appear on every link of every message generated by that class
 * **Method level:** Params specified at method level will appear only on that message
 * **View level:** Views level parameters will take the highest precedence and they will always override all the others

In order to enable Google Analytics params for a given mailer you should simply add a line to a given mailer as in:

```ruby
class UserMailer < ActionMailer::Base
  default :from => 'no-reply@example.com'

  # declare url parameters for this mailer
  google_analytics_mailer utm_source: 'newsletter', utm_medium: 'email' # etc

  # Links in this email will have all links with GA params automatically inserted
  def welcome
    mail(to: 'user@example.com')
  end
end
```

Then in your view generate links as usual:

```erb
<!-- this will produce your-url?utm_medium=email&utm_source=newsletter because of class default params -->
<%= link_to('Read online', newsletter_url) -%>
<!-- local parameters are not overridden, so this produces ?utm_medium=email&utm_source=my_newsletter -->
<%= link_to('Read online', newsletter_url(utm_source: 'my_newsletter')) -%>
```

In order to override params for a specific message you can override params in the method which defines
the message as in:

```ruby
class UserMailer < ActionMailer::Base
  default :from => 'no-reply@example.com'

  # declare url parameters for this mailer
  google_analytics_mailer utm_source: 'newsletter', utm_medium: 'email' # etc

  # Links in this email will have utm_source equal to second_newsletter
  def welcome
    google_analytics_params(utm_source: 'second_newsletter', utm_term: 'welcome2')
    mail(to: 'user@example.com')
  end
end
```

At view level you can override generated parameters using the `with_google_analytics_params` method

```erb
<div class="footer">
  <%- with_google_analytics_params(utm_term: 'footer') do -%>
    <!-- this will override other params and produces ?utm_medium=email&utm_source=newsletter&utm_term=footer -->
    <%= link_to('Read online', newsletter_url) -%>
  <%- end -%>
</div>
```

## Contributing

1. Fork it
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create new Pull Request