ios检测是否有网络连接

去这里http://developer.apple.com/iphone/library/samplecode/Reachability/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007324-Intro-DontLinkElementID_2 下载Reachability.m和Reachability.h，然后添加到你的项目里面，在需要测试网络连接class里面写这样的一个方法

- (BOOL)testConnection {
BOOL result = YES;
Reachability *reach=[Reachability sharedReachability];
[reach setHostName:@“你自己输入一个网址来做ping”];
NetworkStatus status;
status=[reach remoteHostStatus];
if (status == NotReachable) {
result = NO;
} else if (status == ReachableViaCarrierDataNetwork) {
result = YES;
} else if (status == ReachableViaWiFiNetwork) {
result = YES;
}else {
result = NO;
}
return result;
}