Rails - How to access the current environment's host URL?

in my rails app for my environments, i have the following:

config.action_mailer.default_url_options = { :host => '0.0.0.0:3000' }

How can I access that param in a user_mailer?

I want to get开发者_Go百科 what host equals.

Thanks

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ActionMailer::Base.default_url_options[:host]