Action mailer default_url_options

In Rails, default_url_options is a method that allows you to set default options for URLs generated by the url_for method. In the context of an Action Mailer, default_url_options is used to set default options for the URLs used in the email templates.

Here's an example of how you might use default_url_options in an Action Mailer:

class UserMailer < ApplicationMailer
  default_url_options host: 'example.com', protocol: 'https'
end

In this example, the default_url_options method is called on the UserMailer class, and it sets the default host and protocol for URLs generated by the url_for method. This means that any URLs generated by the mailer will have the host example.com and the protocol https.

You can also use default_url_options to set default options for specific routes. For example:

class UserMailer < ApplicationMailer
  default_url_options host: 'example.com', protocol: 'https', only_path: true
end

In this example, the only_path option is set to true, which means that URLs generated by the mailer will only include the path part of the URL, without the host or protocol.

You can also use default_url_options to set default options for specific controllers. For example:

class UserMailer < ApplicationMailer
  default_url_options controller: 'users', action: 'show'
end

In this example, the default_url_options method is called on the UserMailer class, and it sets the default controller and action for URLs generated by the mailer. This means that any URLs generated by the mailer will point to the show action of the users controller.

It's worth noting that default_url_options is a class-level method, so it's called once when the mailer is initialized, and the options are stored as an instance variable. This means that you can't use default_url_options to set options that depend on the instance of the mailer, such as the current user's ID. If you need to set options that depend on the instance of the mailer, you'll need to use a different approach, such as using a helper method or a instance variable.