AFNetworkReachabilityManager可以实现对网络的监听，但是默认只实现了对WiFi网络状态的监听，下面简单介绍如何实现对2G 3G 4G网络状态的区分

1.第一步

修改网络状态的枚举，在AFNetworkReachabilityManager.h文件，修改后的代码如下：

typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
    AFNetworkReachabilityStatusUnknown          = -1,
    AFNetworkReachabilityStatusNotReachable     = 0,
    AFNetworkReachabilityStatusReachableViaWiFi = 1,
    AFNetworkReachabilityStatusReachableVia2G = 2,
    AFNetworkReachabilityStatusReachableVia3G = 3,
    AFNetworkReachabilityStatusReachableVia4G = 4,
};

2.第二步

在AFNetworkReachabilityManager.m文件中进行修改，先引入头文件

#import <CoreTelephony/CTTelephonyNetworkInfo.h>

这个主要用来处理当前网络状态2G 3G 4G
修改如下监听到WWAN部分代码

static AFNetworkReachabilityStatus AFNetworkReachabilityStatusForFlags(SCNetworkReachabilityFlags flags) {
    BOOL isReachable = ((flags & kSCNetworkReachabilityFlagsReachable) != 0);
    BOOL needsConnection = ((flags & kSCNetworkReachabilityFlagsConnectionRequired) != 0);
    BOOL canConnectionAutomatically = (((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) || ((flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0));
    BOOL canConnectWithoutUserInteraction = (canConnectionAutomatically && (flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0);
    BOOL isNetworkReachable = (isReachable && (!needsConnection || canConnectWithoutUserInteraction));

    AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusUnknown;
    if (isNetworkReachable == NO) {
        status = AFNetworkReachabilityStatusNotReachable;
    }
#if TARGET_OS_IPHONE
    else if ((flags & kSCNetworkReachabilityFlagsIsWWAN) != 0) {
        CTTelephonyNetworkInfo * info = [[CTTelephonyNetworkInfo alloc] init];
        NSString *currentRadioAccessTechnology = info.currentRadioAccessTechnology;
        if (currentRadioAccessTechnology) {
            if ([currentRadioAccessTechnology isEqualToString:CTRadioAccessTechnologyLTE]) {
                status =  AFNetworkReachabilityStatusReachableVia4G;
            }
            else if ([currentRadioAccessTechnology isEqualToString:CTRadioAccessTechnologyEdge] || [currentRadioAccessTechnology isEqualToString:CTRadioAccessTechnologyGPRS]) {
                status =  AFNetworkReachabilityStatusReachableVia2G;
            }
            else {
                status =  AFNetworkReachabilityStatusReachableVia3G;
            }
        }
    }
#endif
    else {
        status = AFNetworkReachabilityStatusReachableViaWiFi;
    }
    return status;
}

最后，我们也修改下网络监听的输出吧（当然这步也可以省略），具体代码如下

typedef void (^AFNetworkReachabilityStatusBlock)(AFNetworkReachabilityStatus status);

NSString * AFStringFromNetworkReachabilityStatus(AFNetworkReachabilityStatus status) {
    switch (status) {
        case AFNetworkReachabilityStatusNotReachable:
            return NSLocalizedStringFromTable(@"Not Reachable", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableViaWiFi:
            return NSLocalizedStringFromTable(@"Reachable via WiFi", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableVia2G:
            return NSLocalizedStringFromTable(@"Reachable via 2G", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableVia3G:
            return NSLocalizedStringFromTable(@"Reachable via 3G", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableVia4G:
            return NSLocalizedStringFromTable(@"Reachable via 4G", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusUnknown:
        default:
            return NSLocalizedStringFromTable(@"Unknown", @"AFNetworking", nil);
    }
}