ios Undefined symbols for architecture i386

1、
Undefined symbols for architecture i386:
"_SCNetworkReachabilityCreateWithAddress", referenced from:
"_SCNetworkReachabilityGetFlags", referenced from:
解决办法：添加SystemConfiguration.framework

2.这个是引用NSDataAdditions时出现的bug，

"_deflate", referenced from:
      -[NSData(NSDataAdditions) gzipDeflate] in NSDataAdditions.o
  "_deflateEnd", referenced from:
      -[NSData(NSDataAdditions) gzipDeflate] in NSDataAdditions.o
  "_deflateInit2_", referenced from:
      -[NSData(NSDataAdditions) gzipDeflate] in NSDataAdditions.o
  "_inflate", referenced from:
      -[NSData(NSDataAdditions) gzipInflate] in NSDataAdditions.o
  "_inflateEnd", referenced from:
      -[NSData(NSDataAdditions) gzipInflate] in NSDataAdditions.o
  "_inflateInit2_", referenced from:
      -[NSData(NSDataAdditions) gzipInflate] in NSDataAdditions.o
解决办法：添加libz.dylib类库

3.'libxml/HTMLpraser.h' file not found

这个是一位网友在xcode4.3.2中编译没问题，但是在xcode4.6.3中编译是遇到的，给的解决步骤是

添加libxml2.2.dylib类库
在Build Settings->Other Liner Flags此项中添加-lxml2,如下图

在Build Settings->Header Search Paths项添加/usr/include/libxml2,如下图

据这位网友讲，修复过后报错armv7s，armv7s的问题比较常见的解决办法是在Build Settings->Valid Architectures项中去除armv7s，如果还是未能解决，请谷歌armv7s查找具体解决办法
PS：用第三方类库.a文件时很容易出现无法解决的armv7s问题，尤其是好多类库都比较老，但是苹果的类库和XCode一直在更新，很容易出现未知错误，建议用第三方库时导入.m文件，比较容易解决问题

1. selector警告

   performSelector may cause a leak because its selector is unknown
   触发原因

   SEL sel = @selector(touch:);
   [self performSelector:sel withObject:textField];
   解决办法

   import <objc/message.h>

   SEL sel = @selector(touch:);
   objc_msgSend(self, sel, textField);// textField为touch：后跟的参数，如有多个参数，用','连接即可
   如有问题也可留言大家一起学习解决