关于官方Reachability Demo理解

1. 示例说明：此示例用于演示关于如何使用SystemConfiguratio Reachalility程序接口来判定相关的网络连接状态及状态变化，所以在使用此示例中的Reachability.(h/m)文件于自有的项目中的前提是必须引入SystemConfiguration.framework。

2. 首选分析Reachability.h文件：

-> 首先引入<SystemConfiguration/SystemConfiguration.h>

#import <SystemConfiguration/SystemConfiguration.h>

-> 定义代表网络状态的枚举类型NetworkStatus：

// 定义网络请求可到达状态
typedef enum 
{
    NotReachable = 0,   // 不可到达
    ReachableViaWiFi,   // 通过WiFi可到达
    ReachableViaWWAN    // 通过无线广域网可到达(WWAN，即Wireless Wide Area Network，无线广域网。)
} NetworkStatus;

-> 宏定义关于网络连接变更的通知标识名称：

#define kReachabilityChangedNotification @"kNetworkReachabilityChangedNotification"

-> 定义相关属性：

BOOL localWiFiRef;    
// 用来保存创建测试连接返回的引用
SCNetworkReachabilityRef reachabilityRef;

-> 声明各相关的方法：

// 用于检查网络请求是否可到达指定的主机名
+ (Reachability*) reachabilityWithHostName: (NSString*) hostName;

// 用于检查网络请求是否可到达指定的IP地址
+ (Reachability*) reachabilityWithAddress: (const struct sockaddr_in*) hostAddress;

// 用于检查路由连接是否有效
+ (Reachability*) reachabilityForInternetConnection;

// 用于检查本地的WiFi连接是否有效
+ (Reachability*) reachabilityForLocalWiFi;

// 在当前程序的运行回路中开始监听网络请求可到达的通知
- (BOOL) startNotifier;
- (void) stopNotifier;

// 当前网络请求可到达状态
- (NetworkStatus) currentReachabilityStatus;

// 当前网络请求可到达状态
- (NetworkStatus) currentReachabilityStatus;

// 连接需求
- (BOOL) connectionRequired;

- (void) applicationDidFinishLaunching: (UIApplication* )application 
{
    [[NSNotificationCenter defaultCenter]　　addObserver:self
　　　　　　　　　　　　　　　　　　　　　　　　　　　 selector:@selector(reachabilityChanged:)
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　name:kReachabilityChangedNotification
　　　　　　　　　　　　　　　　　　　　　　　　　　　　　object:nil];　　
    hostReach = [[Reachability reachabilityWithHostName:@"www.apple.com"] retain];
    [hostReach startNotifier];

    internetReach = [[Reachability reachabilityForInternetConnection] retain];
    [internetReach startNotifier];
    [self updateInterfaceWithReachability:internetReach];

    wifiReach = [[Reachability reachabilityForLocalWiFi] retain];
    [wifiReach startNotifier]; 
    [self updateInterfaceWithReachability:wifiReach];

    [window makeKeyAndVisible];
}

- (void)reachabilityChanged:(NSNotification *)note
{
    Reachability *curReach = [note object];
    NSParameterAssert([curReach isKindOfClass:[Reachability class]]);
    [self updateInterfaceWithReachability:curReach];
}

- (void)updateInterfaceWithReachability:(Reachability *)curReach
{
    if (curReach == hostReach)
    {
        [self configureTextField:remoteHostStateField imageView:remoteHostIcon reachability:curReach];
        NetworkStatus netStatus = [curReach currentReachabilityStates];
        BOOL connectionRequired = [curReach connectionRequired];
        
        summaryLabel.hidden = (netStatus != ReachabilityViaWWAN);
        NSString *baseLabel = @"";
        if (connectionRequired)
        {
            baseLabel = @"Cellular data network is available.\n Internet traffic will be routed through it after a connection is established.";
        }
        else
　　　　 {
            baseLabel = @"Cellular data network is active.\n Internet traffic will be routed through it.";
        }
        summaryLabel.text = baseLabel;
    }
    if (curReach == internetReach)
    {
        [self configureTextField:internetConnectionStatusField imageView:internetConnectionIcon reachability:curReach];
    }
    if (curReach == wifiReach)
    {
        [self configureTextField:localWiFiConnectionStatusField imageView:localWiFiConnectionIcon reachability:curReach];
    }
}

- (void)configureTextField:(UITextField *)textField imageView:(UIImageView *)imageView reachability:(Reachability *)curReach
{
    NetworkStatus netStatus = [curReach currentReachabilityStatus];
    BOOL connectionRequired = [curReach connectionRequired];
    NSString *statusString = @"";
    switch (netStatus)
    {
        case NotReachable:
        {
            statusString = @"Access Not Available";
            imageView.image = [UIImage imageNamed:@"stop-32.png"];
            connectionRequired = NO;

            break;
        }
        case ReachableViaWWAN:
        {
            statusString = @"Reachable WWAN";
            imageView.image = [UIImage imageNamed:@"WWAN5.png"];
        
            break;
        }
        case ReachableViaWiFi:
        {
            statusString = @"";
            imageView.image = [UIImage imageNamed:@"Airport.png"];

            break;
        }
    }
    if (connectionRequired)
    {
        statusString = [NSString stringWithFormat:@"%@, Connection Required", statusString];
    }
    textField.text = statusString;
}

. 关于Reachability.m

参考此链接：http://blog.sina.com.cn/s/blog_65a8ab5d010110w5.html

4. 关于Reachability的使用：