JTSReachabilit
An adaptation of Apple's Reachability with some block-based conveniences.
这是一个苹果的网络检测类的改编版本，提供便利的基于block的方法。
Usage
Usage is straightforward.
使用就如其名一样简单。
Singleton
Access the singleton instance of JTSReachabilityResponder via:
你可以通过以下方法来操作单例：
+ (instancetype)sharedInstance;
Or Non-Singleton, if You're Not Into the Whole Singleton Thing
Instantiate an instance of JTSReachabilityResponder via:
你也可以根据某个具体的hostname来作为网络检测的基准：
- (instancytype)initWithOptionalHostname:(NSString *)hostname;
If you don't specify a hostname, there are some edge cases where Apple's networking frameworks will assume there's a valid connection even when there isn't (e.g. when connected to a local WiFi network without a connection to the Internet proper).
如果你没有指定一个hostname，会有一些极端情况导致出错（比方说，你连上了路由器上的wifi，但是这个路由器没有连上网，这个时候你是不能上网的）
Registering Status Change Handlers
An object in your application registers a block to be executed whenever the network status changes between one of the three known states (none, Wi-fi, or cellular) as follows:
一个block对象会因为网络状态的改变而执行（三种状态：没有网络，wifi，cellular）
- (void)someSetupMethod {
JTSReachabilityResponder *responder = [JTSReachabilityResponder sharedInstance];
[responder addHandler:^(JTSNetworkStatus status) {
// Respond to the value of "status"
} forKey:@"MyReachabilityKey"]; }
Your object is responsible for cleaning up after itself, typically in dealloc, as follows:
你也需要在dealloc方法中将这个监听移除掉哦：
- (void)dealloc {
JTSReachabilityResponder *responder = [JTSReachabilityResponder sharedInstance];
[responder removeHandlerForKey:@"MyReachabilityKey"]; }
All blocks are called on the main thread, and must be added or removed on the main thread.
所有的block都是在主线程上面执行的，所以，也必须在主线程上面移除掉。
