Add Set default_url_options For Entire Application as a Rails til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_1009 TILs and counting..._
+_1010 TILs and counting..._
 
 ---
 
@@ -664,6 +664,7 @@ _1009 TILs and counting..._
 - [Select A Select By Selector](rails/select-a-select-by-selector.md)
 - [Select Value For SQL Counts](rails/select-value-for-sql-counts.md)
 - [Serialize With fast_jsonapi In A Rails App](rails/serialize-with-fast-jsonapi-in-a-rails-app.md)
+- [Set default_url_options For Entire Application](rails/set-default-url-options-for-entire-application.md)
 - [Set Schema Search Path](rails/set-schema-search-path.md)
 - [Show Pending Migrations](rails/show-pending-migrations.md)
 - [Show Rails Models With Pry](rails/show-rails-models-with-pry.md)

rails/set-default-url-options-for-entire-application.md

@@ -0,0 +1,30 @@
+# Set default_url_options For Entire Application
+
+There are a [number of
+ways](https://github.com/rails/rails/issues/29992#issuecomment-575464112) to
+set `default_url_options` for the various modules that need them. While the
+development server can infer URL options for the most part, it needs them
+explicitly defined for `ActionMailer`. You may also see the `ArgumentError:
+Missing host to link to! Please provide the :host parameter, set
+default_url_options[:host], or set :only_path to true` error when using a URL
+helper. That's because the `routes` config also needs to know.
+
+Instead of cobbling together default settings in several different places as
+the issues arise, you can define them application-wide like so:
+
+```ruby
+# config/environments/development.rb
+Rails.application.default_url_options = { host: 'localhost', port: 3000 }
+
+Rails.application.configure do
+ # ...
+end
+```
+
+Add the `default_url_options` to `Rails.application` just outside of the
+standard `configure` block in each of your environment config files. Now
+everything should know how to generate full URLs.
+
+Note: I've tested this out in a Rails 6.1 application.
+
+[source](https://discuss.rubyonrails.org/t/define-host-so-absolute-urls-work-in-development-and-test/75085/10)