AFNetworking/AFNetworking/AFNetworkReachabilityManager.m

// AFNetworkReachabilityManager.m
// Copyright (c) 2011–2016 Alamofire Software Foundation ( http://alamofire.org/ )
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#import "AFNetworkReachabilityManager.h"
#if !TARGET_OS_WATCH

#import <netinet/in.h>
#import <netinet6/in6.h>
#import <arpa/inet.h>
#import <ifaddrs.h>
#import <netdb.h>

NSString * const AFNetworkingReachabilityDidChangeNotification = @"com.alamofire.networking.reachability.change";
NSString * const AFNetworkingReachabilityNotificationStatusItem = @"AFNetworkingReachabilityNotificationStatusItem"; // 状态key
// 通知

typedef void (^AFNetworkReachabilityStatusBlock)(AFNetworkReachabilityStatus status);
typedef AFNetworkReachabilityManager * (^AFNetworkReachabilityStatusCallback)(AFNetworkReachabilityStatus status);
// 状态的回调

NSString * AFStringFromNetworkReachabilityStatus(AFNetworkReachabilityStatus status) {
    switch (status) {
        case AFNetworkReachabilityStatusNotReachable:
            return NSLocalizedStringFromTable(@"Not Reachable", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableViaWWAN:
            return NSLocalizedStringFromTable(@"Reachable via WWAN", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusReachableViaWiFi:
            return NSLocalizedStringFromTable(@"Reachable via WiFi", @"AFNetworking", nil);
        case AFNetworkReachabilityStatusUnknown:
        default:
            return NSLocalizedStringFromTable(@"Unknown", @"AFNetworking", nil);
    }
}

// 主要使用了判断网络的枚举， 处理网络的状态
static AFNetworkReachabilityStatus AFNetworkReachabilityStatusForFlags(SCNetworkReachabilityFlags flags) {
    BOOL isReachable = ((flags & kSCNetworkReachabilityFlagsReachable) != 0); // 是否可达
    BOOL needsConnection = ((flags & kSCNetworkReachabilityFlagsConnectionRequired) != 0); // 是否需要连接
    
    BOOL canConnectionAutomatically = (((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) || ((flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0));
    // 是否能够自动连接 ， 这两种方式都是能够自动连接上的
    
    BOOL canConnectWithoutUserInteraction = (canConnectionAutomatically && (flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0);
//     能够连接，并且不想需要用户干涉
    
    BOOL isNetworkReachable = (isReachable && (!needsConnection || canConnectWithoutUserInteraction));

    AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusUnknown;
    if (isNetworkReachable == NO) {
        status = AFNetworkReachabilityStatusNotReachable;
    }
#if	TARGET_OS_IPHONE
    else if ((flags & kSCNetworkReachabilityFlagsIsWWAN) != 0) {
        status = AFNetworkReachabilityStatusReachableViaWWAN;
    }
#endif
    else {
        status = AFNetworkReachabilityStatusReachableViaWiFi;
    }

    return status;
}

/**
 * Queue a status change notification for the main thread.
 *
 * This is done to ensure that the notifications are received in the same order
 * as they are sent. If notifications are sent directly, it is possible that
 * a queued notification (for an earlier status condition) is processed after
 * the later update, resulting in the listener being left in the wrong state.
 */
//网络变化的回调 ， 然后发通知啥的，block回调
// 这里回调到了context的callback里面去的
static void AFPostReachabilityStatusChange(SCNetworkReachabilityFlags flags, AFNetworkReachabilityStatusCallback block) {
    AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusForFlags(flags);
    dispatch_async(dispatch_get_main_queue(), ^{
        AFNetworkReachabilityManager *manager = nil;
        if (block) {
            manager = block(status);
        }
        
//         状态个改变的通知
        NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
        NSDictionary *userInfo = @{ AFNetworkingReachabilityNotificationStatusItem: @(status) };
        [notificationCenter postNotificationName:AFNetworkingReachabilityDidChangeNotification object:manager userInfo:userInfo];
    });
}

// 状态的回调
static void AFNetworkReachabilityCallback(SCNetworkReachabilityRef __unused target, SCNetworkReachabilityFlags flags, void *info) {
    AFPostReachabilityStatusChange(flags, (__bridge AFNetworkReachabilityStatusCallback)info);
}

// block的拷贝，这个愿妈妈定义的宏
static const void * AFNetworkReachabilityRetainCallback(const void *info) {
    return Block_copy(info);
}

static void AFNetworkReachabilityReleaseCallback(const void *info) {
    if (info) {
        Block_release(info);
    }
}

@interface AFNetworkReachabilityManager ()

@property (readonly, nonatomic, assign) SCNetworkReachabilityRef networkReachability; // 网络可达的上下文
@property (readwrite, nonatomic, assign) AFNetworkReachabilityStatus networkReachabilityStatus; // 网络状态
@property (readwrite, nonatomic, copy) AFNetworkReachabilityStatusBlock networkReachabilityStatusBlock; //网络状态block
@end

@implementation AFNetworkReachabilityManager

+ (instancetype)sharedManager {
    static AFNetworkReachabilityManager *_sharedManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _sharedManager = [self manager];
    });

    return _sharedManager;
}

// 通过域名来获取对象
+ (instancetype)managerForDomain:(NSString *)domain {
//     创建上下文
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, [domain UTF8String]);

    AFNetworkReachabilityManager *manager = [[self alloc] initWithReachability:reachability];
    
    CFRelease(reachability); // 必须释放掉

    return manager;
}

// 通过ip地址来获取对象
+ (instancetype)managerForAddress:(const void *)address {
    SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithAddress(kCFAllocatorDefault, (const struct sockaddr *)address);
    AFNetworkReachabilityManager *manager = [[self alloc] initWithReachability:reachability];

    CFRelease(reachability);
    
    return manager;
}

// 默认是通过ip地址来获取对象
+ (instancetype)manager
{
//  iOS 9 之后为啥子使用了ipv6，
//  这个地方其实直接使用 后者应该也是没有问题的
#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 90000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 101100)
    struct sockaddr_in6 address;
    bzero(&address, sizeof(address));
    address.sin6_len = sizeof(address);
    address.sin6_family = AF_INET6;
#else
    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_len = sizeof(address);
    address.sin_family = AF_INET;
#endif
    return [self managerForAddress:&address];
}

// 初始化状态为unknown
- (instancetype)initWithReachability:(SCNetworkReachabilityRef)reachability {
    self = [super init];
    if (!self) {
        return nil;
    }

    _networkReachability = CFRetain(reachability); // 持有，因为外面释放了
    self.networkReachabilityStatus = AFNetworkReachabilityStatusUnknown;

    return self;
}

- (instancetype)init
{
    @throw [NSException exceptionWithName:NSGenericException
                                   reason:@"`-init` unavailable. Use `-initWithReachability:` instead"
                                 userInfo:nil];
    return nil;
}

- (void)dealloc {
    [self stopMonitoring];
    
    if (_networkReachability != NULL) {
        CFRelease(_networkReachability);
    }
}

#pragma mark -

// 判断是否可达， wifi还是数据
- (BOOL)isReachable {
    return [self isReachableViaWWAN] || [self isReachableViaWiFi];
}

- (BOOL)isReachableViaWWAN {
    return self.networkReachabilityStatus == AFNetworkReachabilityStatusReachableViaWWAN;
}

- (BOOL)isReachableViaWiFi {
    return self.networkReachabilityStatus == AFNetworkReachabilityStatusReachableViaWiFi;
}

#pragma mark -

// 开始检测
- (void)startMonitoring {
    [self stopMonitoring];

    if (!self.networkReachability) {
        return;
    }

    __weak __typeof(self)weakSelf = self;

//     注册有关的回调
    AFNetworkReachabilityStatusCallback callback = ^(AFNetworkReachabilityStatus status) {
        __strong __typeof(weakSelf)strongSelf = weakSelf;

        // 获取有关的状态，并且回调
        strongSelf.networkReachabilityStatus = status;
        if (strongSelf.networkReachabilityStatusBlock) {
            strongSelf.networkReachabilityStatusBlock(status);
        }
        
        return strongSelf;
    };

//  一个是数据会带哦， 一个是可达性的回调
//AFPostReachabilityStatusChange ——>callback ,最后的数据还是会到这个callback里面处理
    SCNetworkReachabilityContext context = {0, (__bridge void *)callback, AFNetworkReachabilityRetainCallback, AFNetworkReachabilityReleaseCallback, NULL};
    
    SCNetworkReachabilitySetCallback(self.networkReachability, AFNetworkReachabilityCallback, &context);
//     runloop里面处理
    SCNetworkReachabilityScheduleWithRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
    
//     开始的一个防止处理
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0),^{
        SCNetworkReachabilityFlags flags;
        if (SCNetworkReachabilityGetFlags(self.networkReachability, &flags)) {
            AFPostReachabilityStatusChange(flags, callback);
        }
    });
}

// 停止检测以及消费会带哦
- (void)stopMonitoring {
    if (!self.networkReachability) {
        return;
    }

    SCNetworkReachabilityUnscheduleFromRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
    NSLog(@"self newwork res:%@",self.networkReachability);
}

#pragma mark -

- (NSString *)localizedNetworkReachabilityStatusString {
    return AFStringFromNetworkReachabilityStatus(self.networkReachabilityStatus);
}

#pragma mark -

- (void)setReachabilityStatusChangeBlock:(void (^)(AFNetworkReachabilityStatus status))block {
    self.networkReachabilityStatusBlock = block;
}

#pragma mark - NSKeyValueObserving

// 处理根据状态而发生变化的属性
+ (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key {
    if ([key isEqualToString:@"reachable"] || [key isEqualToString:@"reachableViaWWAN"] || [key isEqualToString:@"reachableViaWiFi"]) {
        return [NSSet setWithObject:@"networkReachabilityStatus"];
    }

    return [super keyPathsForValuesAffectingValueForKey:key];
}

@end
#endif