关于获取当前网络是属于2G还是3G(极其简单)

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提供的例子：Reachability

通过如下的代码：

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 = ReachableVia3G;
                if((flags & kSCNetworkReachabilityFlagsConnectionRequired) == kSCNetworkReachabilityFlagsConnectionRequired)
                {
                    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。

作者：Rush.D.Xzj

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