去苹果API里搜索Reachability，下载Demo(点击左上角Download Sample Code 即可下载)，把demo里的Reachability.h和Reachability.m拖到自己的工程里。也可以在百度里面搜索”Reachability”，然后下载，不一定非要到苹果官网去下载。

但是使用Reachability有一个问题，就是它只能判断当前是Wifi或者手机自带网络，没有办法详细得判断2G、3G、4G。
如果确定为手机自带网络，这时可以使用系统自带的API来判断是2G、3G还是4G，这就要使用到CTTelephonyNetworkInfo这类，记得在工程添加CoreTelephony.framework

记得导入头文件：

import "Reachability.h"

import <CoreTelephony/CTCarrier.h>

import <CoreTelephony/CTTelephonyNetworkInfo.h>

#if (CC_TARGET_PLATFORM == CC_PLATFORM_IOS)

#import "Reachability.h"

#include <sys/param.h>

#include <sys/mount.h>

 #endif

下面附上我在项目中使用的代码：

+ (NSString *)getNetconnType{ NSString *netconnType = @""; Reachability *reach = [Reachability reachabilityWithHostName:@"www.apple.com"]; switch ([reach currentReachabilityStatus]) { case NotReachable:// 没有网络 { netconnType = @"no network"; } break; case ReachableViaWiFi:// Wifi { netconnType = @"Wifi"; } break; case ReachableViaWWAN:// 手机自带网络 { // 获取手机网络类型 CTTelephonyNetworkInfo *info = [[CTTelephonyNetworkInfo alloc] init]; NSString *currentStatus = info.currentRadioAccessTechnology; if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyGPRS"]) { netconnType = @"GPRS"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyEdge"]) { netconnType = @"2.75G EDGE"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyWCDMA"]){ netconnType = @"3G"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyHSDPA"]){ netconnType = @"3.5G HSDPA"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyHSUPA"]){ netconnType = @"3.5G HSUPA"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMA1x"]){ netconnType = @"2G"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORev0"]){ netconnType = @"3G"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORevA"]){ netconnType = @"3G"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyCDMAEVDORevB"]){ netconnType = @"3G"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyeHRPD"]){ netconnType = @"HRPD"; }else if ([currentStatus isEqualToString:@"CTRadioAccessTechnologyLTE"]){ netconnType = @"4G"; } } break; default: break; } return netconnType; }