看了YYReachability的代码，学习了几点记录下，与大家分享。

WWAN的分类

一直在说的2G，3G，4G网络，看了代码后才知道，原来移动网络的分类是根据频率来分的：

typedef NS_ENUM(NSUInteger, YYReachabilityWWANStatus) {
    YYReachabilityWWANStatusNone  = 0, ///< Not Reachable vis WWAN
    YYReachabilityWWANStatus2G = 2, ///< Reachable via 2G (GPRS/EDGE)       10~100Kbps
    YYReachabilityWWANStatus3G = 3, ///< Reachable via 3G (WCDMA/HSDPA/...) 1~10Mbps
    YYReachabilityWWANStatus4G = 4, ///< Reachable via 4G (eHRPD/LTE)       100Mbps
};

苹果官方提供的网络分类：

dic = @{CTRadioAccessTechnologyGPRS : @(YYReachabilityWWANStatus2G),  // 2.5G   171Kbps
                CTRadioAccessTechnologyEdge : @(YYReachabilityWWANStatus2G),  // 2.75G  384Kbps
                CTRadioAccessTechnologyWCDMA : @(YYReachabilityWWANStatus3G), // 3G     3.6Mbps/384Kbps
                CTRadioAccessTechnologyHSDPA : @(YYReachabilityWWANStatus3G), // 3.5G   14.4Mbps/384Kbps
                CTRadioAccessTechnologyHSUPA : @(YYReachabilityWWANStatus3G), // 3.75G  14.4Mbps/5.76Mbps
                CTRadioAccessTechnologyCDMA1x : @(YYReachabilityWWANStatus3G), // 2.5G
                CTRadioAccessTechnologyCDMAEVDORev0 : @(YYReachabilityWWANStatus3G),
                CTRadioAccessTechnologyCDMAEVDORevA : @(YYReachabilityWWANStatus3G),
                CTRadioAccessTechnologyCDMAEVDORevB : @(YYReachabilityWWANStatus3G),
                CTRadioAccessTechnologyeHRPD : @(YYReachabilityWWANStatus3G),
                CTRadioAccessTechnologyLTE : @(YYReachabilityWWANStatus4G)}; // LTE:3.9G 150M/75M  LTE-Advanced:4G 300M/150M

通过属性

@property (nonatomic, readonly, retain, nullable) NSString* currentRadioAccessTechnology __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_7_0);

返回。

网络监控

针对网络改变的主要代码是：

SCNetworkReachabilityContext context = { 0, (__bridge void *)self, NULL, NULL, NULL };
SCNetworkReachabilitySetCallback(self.ref, YYReachabilityCallback, &context);
SCNetworkReachabilitySetDispatchQueue(self.ref, [self.class sharedQueue]);

使用回调方法来通知网络的变化。

静态方法

使用了C语言的静态函数来传递函数指针。

SCNetworkReachabilitySetCallback(self.ref, YYReachabilityCallback, &context);

YYReachabilityCallback为申明的静态函数

static void YYReachabilityCallback(SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void *info) {
    YYReachability *self = ((__bridge YYReachability *)info);
    if (self.notifyBlock) {
        dispatch_async(dispatch_get_main_queue(), ^{
            self.notifyBlock(self);
        });
    }
}

与AFNetworking库中的AFNetworkReachabilityManager实现逻辑一致。

测试

编写了测试代码：

- (void)testReachability
{
    YYReachability *reachability = [YYReachability reachability];

    reachability.notifyBlock = ^(YYReachability *reachability){
        NSLog(@"reachability.flags is %d.", reachability.flags);
        NSLog(@"reachability.status is %lu.", (unsigned long)reachability.status);
        NSLog(@"reachability.wwanStatus is %lu.", (unsigned long)reachability.wwanStatus);
    };

    self.reachability = reachability;
}

必须申明实例变量，如果是临时编码，将不会执行block。

• 从无网，切换到4G，

2017-09-25 19:09:46.864040+0800 RecordTechnology[12013:1154192] reachability.flags is 262147.
2017-09-25 19:09:46.864369+0800 RecordTechnology[12013:1154192] reachability.status is 1.
2017-09-25 19:09:46.864541+0800 RecordTechnology[12013:1154192] reachability.wwanStatus is 4.

切换到wifi，

2017-09-25 19:11:36.266635+0800 RecordTechnology[12013:1154192] reachability.flags is 2.
2017-09-25 19:11:36.282290+0800 RecordTechnology[12013:1154192] reachability.status is 2.
2017-09-25 19:11:36.291125+0800 RecordTechnology[12013:1154192] reachability.wwanStatus is 4.

关闭4G，不打印日志
关闭wifi。

2017-09-25 19:11:56.093725+0800 RecordTechnology[12013:1154192] reachability.flags is 0.
2017-09-25 19:11:56.094497+0800 RecordTechnology[12013:1154192] reachability.status is 0.
2017-09-25 19:11:56.094859+0800 RecordTechnology[12013:1154192] reachability.wwanStatus is 4.

网络切换显示正常。

// END