From 4288469d3e867b84f44e71e254ce0d3bd9fe22b2 Mon Sep 17 00:00:00 2001
From: Stephan Besser <reskume@users.noreply.github.com>
Date: Thu, 17 Oct 2019 21:23:44 +0200
Subject: [PATCH] Fixes "Cannot read property 'app' of undefined" on nuxt build

The provided example works flawlessly in dev mode but when "nuxt build" is run, the build will fail with an error "Cannot read property 'app' of undefined" since the renderer is not available yet. By using the 'render:before' hook to assure that the renderer is available, it works as expected. This may not be the best solution but worked for me.
---
 examples/with-sockets/io/index.js | 34 ++++++++++++++++---------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/examples/with-sockets/io/index.js b/examples/with-sockets/io/index.js
index 753039a53080..687f16b6518e 100644
--- a/examples/with-sockets/io/index.js
+++ b/examples/with-sockets/io/index.js
@@ -2,23 +2,25 @@ import http from 'http'
 import socketIO from 'socket.io'
 
 export default function () {
-  const server = http.createServer(this.nuxt.renderer.app)
-  const io = socketIO(server)
+  this.nuxt.hook('render:before', (renderer) => {
+    const server = http.createServer(this.nuxt.renderer.app)
+    const io = socketIO(server)
 
-  // overwrite nuxt.server.listen()
-  this.nuxt.server.listen = (port, host) => new Promise(resolve => server.listen(port || 3000, host || 'localhost', resolve))
-  // close this server on 'close' event
-  this.nuxt.hook('close', () => new Promise(server.close))
+    // overwrite nuxt.server.listen()
+    this.nuxt.server.listen = (port, host) => new Promise(resolve => server.listen(port || 3000, host || 'localhost', resolve))
+    // close this server on 'close' event
+    this.nuxt.hook('close', () => new Promise(server.close))
 
-  // Add socket.io events
-  const messages = []
-  io.on('connection', (socket) => {
-    socket.on('last-messages', function (fn) {
-      fn(messages.slice(-50))
+    // Add socket.io events
+    const messages = []
+    io.on('connection', (socket) => {
+      socket.on('last-messages', function (fn) {
+        fn(messages.slice(-50))
+      })
+      socket.on('send-message', function (message) {
+        messages.push(message)
+        socket.broadcast.emit('new-message', message)
+      })
     })
-    socket.on('send-message', function (message) {
-      messages.push(message)
-      socket.broadcast.emit('new-message', message)
-    })
-  })
+  }
 }