判断网络所属2G、3G、WiFi

中国的iphone网络是区分2G和3G，要想获取当前的网络状态一直没有一个好的方法，网上给的例子也不尽让人满意最近闲来无事，仔细的研究Apple提供的

 Reachability *reach = [Reachability reachabilityWithHostName:@"www.apple.com"];
 NSLog(@"%d", [reach currentReachabilityStatus]); 
 return;

在currentReachabilityStatus函数中，我们注意到这样的输出

static void PrintReachabilityFlags(SCNetworkReachabilityFlags flags, c*****t char* comment)
{
#if kShouldPrintReachabilityFlags
NSLog(@"Reachability Flag Status: %c%c %c%c%c%c%c%c%c %s\n",
	 (flags & kSCNetworkReachabilityFlagsIsWWAN) ? 'W' : '-', 
	 (flags & kSCNetworkReachabilityFlagsReachable) ? 'R' : '-',
	 (flags & kSCNetworkReachabilityFlagsTransientConnection) ? 't' : '-',
	 (flags & kSCNetworkReachabilityFlagsConnectionRequired) ? 'c' : '-',
	 (flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) ? 'C' : '-', 
	 (flags & kSCNetworkReachabilityFlagsInterventionRequired) ? 'i' : '-',
	 (flags & kSCNetworkReachabilityFlagsConnectionOnDemand) ? 'D' : '-', 
	 (flags & kSCNetworkReachabilityFlagsIsLocalAddress) ? 'l' : '-',
	 (flags & kSCNetworkReachabilityFlagsIsDirect) ? 'd' : '-',
	 comment 
	 );
#endif
}

当是wifi的时候输出R

当是3G的时候输出Rt

当是联通2G或者是移动的时候输出Rtc

在头文件定义如下：

typedef enum 
{ 
 	NotReachable = 0,
 	ReachableViaWiFi, 
 	ReachableVia3G, 
 	ReachableVia2G,//当前无法区分是联通的2G还是移动的2G
} NetworkStatus;

因此我就是以这个为判断条件的，重写Reachability的函数：

- (NetworkStatus) networkStatusForFlags: (SCNetworkReachabilityFlags) flags
{
	if ((flags & kSCNetworkReachabilityFlagsReachable) == 0)
	{ 
		 return NotReachable;
	}
	BOOL retVal = NotReachable;
	if ((flags & kSCNetworkReachabilityFlagsConnectionRequired) == 0)
	{ 
		 // if target host is reachable and no connection is required
 		// then we'll assume (for now) that your on Wi-Fi 
 		retVal = ReachableViaWiFi;
	}
	if (
		((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) || 
 		(flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0
	)
	{
 		// ... and the connection is on-demand (or on-traffic) if the
 		// calling application is using the CFSocketStream or higher APIs
		 if ((flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0) 
 		{ 
 			// ... and no [user] intervention is needed 
 			retVal = ReachableViaWiFi; 
 		} 
 	}
	if ((flags & kSCNetworkReachabilityFlagsIsWWAN) == kSCNetworkReachabilityFlagsIsWWAN) 
	{ 
 		retVal = ReachableVia3G;
 		if((flags & kSCNetworkReachabilityFlagsReachable) == kSCNetworkReachabilityFlagsReachable) 
		{ 
			if((flags & kSCNetworkReachabilityFlagsTransientConnection) == kSCNetworkReachabilityFlagsTransientConnection)
 			{ 
 				retVal = ReachableVia2G;
 			} 
 		} 
	}
	return retVal;
}

这样就可以正确的区分是2G，3G，wifi网络，这只支持中国地区，其他地区未考虑。