Link to Apple site association docs

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1233 TILs and counting..._
+_1234 TILs and counting..._
 
 ---
 
@@ -794,6 +794,7 @@ _1233 TILs and counting..._
 - [Replace An Index With A Unique Index](rails/replace-an-index-with-a-unique-index.md)
 - [Rescue From](rails/rescue-from.md)
 - [Rescue From With A Separate Method](rails/rescue-from-with-a-separate-method.md)
+- [Respond With JSON Regardless of Content Type](rails/respond-with-json-regardless-of-content-type.md)
 - [Retrieve An Object If It Exists](rails/retrieve-an-object-if-it-exists.md)
 - [Rollback A Specific Migration Out Of Order](rails/rollback-a-specific-migration-out-of-order.md)
 - [Rounding Numbers With Precision](rails/rounding-numbers-with-precision.md)

rails/respond-with-json-regardless-of-content-type.md

@@ -0,0 +1,34 @@
+# Respond With JSON Regardless Of Content Type
+
+Let's say you want to serve some JSON from an endpoint (for example, you might
+be serving [the `apple-app-site-association` file for iOS Universal
+Links](https://developer.apple.com/documentation/xcode/supporting-associated-domains)).
+Regardless of whether the endpoint is requested as JSON (`application/json`),
+HTML (`text/html`), or something else (`plain/text`), you want to respond with
+JSON.
+
+The [`format#any`
+method](https://api.rubyonrails.org/classes/ActionController/MimeResponds.html)
+can be used when defining the `respond_to` block. This tells the controller
+that _any_ mimetype is accepted.
+
+```ruby
+def show
+  respond_to do |format|
+    format.any do
+      render params[:page],
+        formats: 'json',
+        content_type: "application/json",
+        layout: false
+    end
+  end
+end
+```
+
+The other important element in this is `formats: 'json'` which helps Rails find
+your `<template_name>.json.erb` file in the `views` directory.
+
+Though I cannot find any documentation for it, `format.all` appears to work the
+same as `format.any` as described in the above example.
+
+h/t Dillon Hafer