From 04f179fe88d407156ea40b592fbd0475b3535616 Mon Sep 17 00:00:00 2001
From: dblock <dblock@dblock.org>
Date: Wed, 17 Jun 2015 14:32:45 -0400
Subject: [PATCH] Added note on upgrading from #1029.

---
 UPGRADING.md | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/UPGRADING.md b/UPGRADING.md
index 95a2a6c9f..88bc7b8b3 100644
--- a/UPGRADING.md
+++ b/UPGRADING.md
@@ -3,6 +3,34 @@ Upgrading Grape
 
 ### Upgrading to >= 0.12.0
 
+#### Changes in middleware
+
+The Rack response object is no longer converted to an array by the formatter, enabling streaming. If your custom middleware is accessing `@app_response`, update it to expect a `Rack::Response` instance instead of an array.
+
+For example,
+
+```ruby
+class CacheBusterMiddleware < Grape::Middleware::Base
+  def after
+    @app_response[1]['Expires'] = Time.at(0).utc.to_s
+    @app_response
+  end
+end
+```
+
+becomes
+
+```ruby
+class CacheBusterMiddleware < Grape::Middleware::Base
+  def after
+    @app_response.headers['Expires'] = Time.at(0).utc.to_s
+    @app_response
+  end
+end
+```
+
+See [#1029](https://github.com/intridea/grape/pull/1029) for more information.
+
 #### Changes in present
 
 Using `present` with objects that responded to `merge` would cause early evaluation of the represented object, with unexpected side-effects, such as missing parameters or environment within rendering code. Grape now only merges represented objects with a previously rendered body, usually when multiple `present` calls are made in the same route.