From edd5c85ce92f551747bfcd0cf2fa1a5ac5d8fd97 Mon Sep 17 00:00:00 2001
From: alsotang <alsotang@gmail.com>
Date: Sat, 18 Oct 2014 01:32:14 +0800
Subject: [PATCH] Update 17_Optional_Chaining.md

---
 source/chapter2/17_Optional_Chaining.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/chapter2/17_Optional_Chaining.md b/source/chapter2/17_Optional_Chaining.md
index 841e34db..c8e90811 100755
--- a/source/chapter2/17_Optional_Chaining.md
+++ b/source/chapter2/17_Optional_Chaining.md
@@ -200,7 +200,7 @@ func printNumberOfRooms(){
 如果你利用可选链调用此方法，这个方法的返回值类型将是`Void?`，而不是`Void`，因为当通过可选链调用方法时返回值总是可选类型（optional type）。即使这个方法本身没有定义返回值，你也可以使用`if`语句来检查是否能成功调用`printNumberOfRooms`方法：如果方法通过可选链调用成功，`printNumberOfRooms`的隐式返回值将会是`Void`，如果没有成功，将返回`nil`：
 
 ```swift
-if john.residence?.printNumberOfRooms() {
+if john.residence?.printNumberOfRooms?() {
     println("It was possible to print the number of rooms.")
 } else {
     println("It was not possible to print the number of rooms.")