#import "Reachability.h"

(1)使用同步的方式是比較簡單,通過代碼檢查網絡：

Reachability *reach = [Reachability reachabilityForInternetConnection];

NetworkStatus status = [reach currentReachabilityStatus];

(2)通過檢查某個主機能否訪問來判斷當前網絡是否可用：

Reachability *reach = [Reachability reachabilityWithHostName:@“www.baidu.com”];

NetworkStatus status = [reach currentReachabilityStatus]; ?

ReachableViaWWAN ?3G 網絡

ReachableViaWiFi ? WiFi網絡

NotReachable ?無網絡

（3）實時監測網絡狀態

@property(nonatomic,strong)Reachability*reachability;

- (BOOL)application:(UIApplication*)application didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(netStatusChanged:)name:kReachabilityChangedNotification object:nil];

self.reachability= [ReachabilityreachabilityWithHostName:@"www.baidu.com"];

[self.reachability startNotifier];

}

-(void)netStatusChanged:(NSNotification*)notification{

Reachability*currentStatus = [notificationobject];

NSParameterAssert([currentStatus isKindOfClass:[Reachability class]]);

NetworkStatus status = [currentStatus currentReachabilityStatus];

if(status==NotReachable) {

UIAlertView*alert = [[UIAlertView alloc]initWithTitle:@"溫馨提示"message:@"網絡不可用"delegate:nil cancelButtonTitle:@"確定"otherButtonTitles:nil];

[alert show];

return;

}

}