从Git库下载

https://github.com/tonymillion/Reachability

把两个文件Reachability.h 和 Reachability.m文件添加到工程中。

添加框架支持SystemConfiguration.framework

添加头文件声明：

@class Reachability;

@interface AppDelegate : UIResponder <UIApplicationDelegate>
{
    UINavigationController *_navigationController;
    Reachability  *hostReach;
}

@property (strong, nonatomic) UIWindow *window;

@property (strong, nonatomic) UIViewController *viewController;
@property (strong, nonatomic) UINavigationController *navigationController;
@end

AppDelegate.m实现文件中

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 方法中加入如下代码

 [self netWorkChecker];

添加网络检测代码

#pragma mark network check
-(void)netWorkChecker
{
    hostReach = [Reachability reachabilityWithHostname:@"www.apple.com"];
    switch ([hostReach currentReachabilityStatus]) {
        case NotReachable:
            NSLog(@"没有网络连接");
            // 没有网络连接
            break;
        case ReachableViaWWAN:
            // 使用3G网络
            NSLog(@"使用3G网络");
            break;
        case ReachableViaWiFi:
            // 使用WiFi网络
            NSLog(@"使用WiFi网络");
            break;
    }
    //


}

添加网络变化的通知

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 方法中加入如下代码

 [self addNetWorkChangeNotification];

-(void)addNetWorkChangeNotification
{
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(reachabilityChanged:)
                                                 name: kReachabilityChangedNotification
                                               object: nil];
    hostReach = [Reachability reachabilityWithHostname:@"www.google.com"]  ;
    [hostReach startNotifier];
}
- (void)reachabilityChanged:(NSNotification *)note
{
    Reachability* curReach = [note object];
    NSParameterAssert([curReach isKindOfClass: [Reachability class]]);
    NetworkStatus status = [curReach currentReachabilityStatus];
    NSLog(@"reachabilityChanged delegate NotReachable : %d ", status);

}