此文章对AFNetworkReachabilityManager的源码做一些阅读记录和个人的理解.
AFNetworkReachabilityManager个人理解为是对SCNetworkReachabilityRef的相关封装实现的. 在讲解AFNetworkReachabilityManager之前, 需要先对SCNetworkReachabilityRef有一些了解, 附上SCNetworkReachabilityRef监测网络状态.
AFNetworkReachabilityManager对网络的监测使用如下:
AFNetworkReachabilityManager *networkReachManager = [AFNetworkReachabilityManager sharedManager];
[networkReachManager setReachabilityStatusChangeBlock:^(AFNetworkReachabilityStatus status) {
NSLog(@"%zd", status);
}];
// 开始监测网络
[networkReachManager startMonitoring];
当网络状态发生变化时就会执行block, 将网络状态AFNetworkReachabilityStatus返回给我们.
AFNetworkReachabilityManager.h文件
/**
网络类型
- AFNetworkReachabilityStatusUnknown: 未知网络
- AFNetworkReachabilityStatusNotReachable: 网络不可达, 无网络
- AFNetworkReachabilityStatusReachableViaWWAN: 手机网络
- AFNetworkReachabilityStatusReachableViaWiFi: WiFi
*/
typedef NS_ENUM(NSInteger, AFNetworkReachabilityStatus) {
AFNetworkReachabilityStatusUnknown = -1,
AFNetworkReachabilityStatusNotReachable = 0,
AFNetworkReachabilityStatusReachableViaWWAN = 1,
AFNetworkReachabilityStatusReachableViaWiFi = 2,
};
对外提供四种网络状态的枚举值.
/**
The current network reachability status.
当前网络状态
*/
@property (readonly, nonatomic, assign) AFNetworkReachabilityStatus networkReachabilityStatus;
/**
Whether or not the network is currently reachable.
网络是否可用
*/
@property (readonly, nonatomic, assign, getter = isReachable) BOOL reachable;
/**
Whether or not the network is currently reachable via WWAN.
当前连接是否是WWAN
*/
@property (readonly, nonatomic, assign, getter = isReachableViaWWAN) BOOL reachableViaWWAN;
/**
Whether or not the network is currently reachable via WiFi.
当前连接是否是WiFi
*/
@property (readonly, nonatomic, assign, getter = isReachableViaWiFi) BOOL reachableViaWiFi;
在.h文件中对外提供了4个只读属性, 并且给出了对应的getter方法.
+ (instancetype)sharedManager;
+ (instancetype)manager;
+ (instancetype)managerForDomain:(NSString *)domain;
+ (instancetype)managerForAddress:(const void *)address;
- (instancetype)initWithReachability:(SCNetworkReachabilityRef)reachability NS_DESIGNATED_INITIALIZER;
- (nullable instancetype)init NS_UNAVAILABLE;
提供几个初始化方法, 创建实例对象.
/**
Starts monitoring for changes in network reachability status.
开始监听
*/
- (void)startMonitoring;
/**
Stops monitoring for changes in network reachability status.
结束监听
*/
- (void)stopMonitoring;
/**
Returns a localized string representation of the current network reachability status.
返回一个网络状态的字符串
*/
- (NSString *)localizedNetworkReachabilityStatusString;
/**
Sets a callback to be executed when the network availability of the `baseURL` host changes.
@param block A block object to be executed when the network availability of the `baseURL` host changes.. This block has no return value and takes a single argument which represents the various reachability states from the device to the `baseURL`.
网络状态改变的回调
监听网络状态的改变有两种方法:1.是实现这个block 2.是监听通知
*/
- (void)setReachabilityStatusChangeBlock:(nullable void (^)(AFNetworkReachabilityStatus status))block;
/**
Posted when network reachability changes.
This notification assigns no notification object. The `userInfo` dictionary contains an `NSNumber` object under the `AFNetworkingReachabilityNotificationStatusItem` key, representing the `AFNetworkReachabilityStatus` value for the current network reachability.
@warning In order for network reachability to be monitored, include the `SystemConfiguration` framework in the active target's "Link Binary With Library" build phase, and add `#import ` to the header prefix of the project (`Prefix.pch`).
网络状态改变时 发送的通知
在userInfo下有以AFNetworkingReachabilityNotificationStatusItem为key的一个NSNumber类型的值, 这个值对应着AFNetworkReachabilityStatus枚举, 反应网络状态
FOUNDATION_EXPORT主要用于定义常量
*/
FOUNDATION_EXPORT NSString * const AFNetworkingReachabilityDidChangeNotification;
FOUNDATION_EXPORT NSString * const AFNetworkingReachabilityNotificationStatusItem;
/**
Returns a localized string representation of an `AFNetworkReachabilityStatus` value.
这个是定义的一个C语言函数, 返回本地化的status字符串
*/
FOUNDATION_EXPORT NSString * AFStringFromNetworkReachabilityStatus(AFNetworkReachabilityStatus status);
定义了两个通知的名称, 当网络状态改变时发出的通知, 接收的通知中会有一个userInfo, 可根据key为AFNetworkingReachabilityNotificationStatusItem取出通知的内容.
我们可以借鉴AFN中通知的实现, 在开发中可以将通知的key定义到一个专门管理常量的文件中, 按照不同的模块进行划分.
AFNetworkReachabilityManager.m文件
// 一个静态字符串, 网络状态发生变化时发出的通知 对应.h
NSString * const AFNetworkingReachabilityDidChangeNotification = @"com.alamofire.networking.reachability.change";
// 网络状态发生变化时发出通知, 携带的数据
NSString * const AFNetworkingReachabilityNotificationStatusItem = @"AFNetworkingReachabilityNotificationStatusItem";
// 将枚举类型转换成字符串(这是对在.h中声明的实现)
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);
}
}
对在.h文件中定义的常量的赋值和函数的实现.
// 定义block类型, 当网络状态改变时调用的block
typedef void (^AFNetworkReachabilityStatusBlock)(AFNetworkReachabilityStatus status);
static AFNetworkReachabilityStatus AFNetworkReachabilityStatusForFlags(SCNetworkReachabilityFlags flags) {
BOOL isReachable = ((flags & kSCNetworkReachabilityFlagsReachable) != 0);
BOOL needsConnection = ((flags & kSCNetworkReachabilityFlagsConnectionRequired) != 0);
BOOL canConnectionAutomatically = (((flags & kSCNetworkReachabilityFlagsConnectionOnDemand ) != 0) || ((flags & kSCNetworkReachabilityFlagsConnectionOnTraffic) != 0));
BOOL canConnectWithoutUserInteraction = (canConnectionAutomatically && (flags & kSCNetworkReachabilityFlagsInterventionRequired) == 0);
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;
}
根据SCNetworkReachabilityFlags这个网络标记转换成AFN中的网络状态
static修饰全局, 只能在当前文件使用
在我们开发的过程中经常会使用私有方法, 将私有方法写成c语言函数的形式的好处(个人理解)(static void functionName(){}):
1.在文件的最前边, 方便查找
2.可以使用内联函数, 提高效率
static void AFPostReachabilityStatusChange(SCNetworkReachabilityFlags flags, AFNetworkReachabilityStatusBlock block) {
AFNetworkReachabilityStatus status = AFNetworkReachabilityStatusForFlags(flags);
dispatch_async(dispatch_get_main_queue(), ^{
if (block) {
block(status);
}
NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
NSDictionary *userInfo = @{ AFNetworkingReachabilityNotificationStatusItem: @(status) };
[notificationCenter postNotificationName:AFNetworkingReachabilityDidChangeNotification object:nil userInfo:userInfo];
});
}
监听网络状态的改变有两种, 一种是实现setReachabilityStatusChangeBlock:中的block, 另一种是监听通知AFNetworkingReachabilityDidChangeNotification, 此方法将监听网络状态改变的两种方式封装到一个函数中, 在主队列中异步执行. 这种方法也是值得学习的地方.
static void AFNetworkReachabilityCallback(SCNetworkReachabilityRef __unused target, SCNetworkReachabilityFlags flags, void *info) {
AFPostReachabilityStatusChange(flags, (__bridge AFNetworkReachabilityStatusBlock)info);
}
这个函数直接调用上边的函数.
static const void * AFNetworkReachabilityRetainCallback(const void *info) {
return Block_copy(info);
}
static void AFNetworkReachabilityReleaseCallback(const void *info) {
if (info) {
Block_release(info);
}
}
void *个人理解为OC中的id类型, 可以指向任何类型. block其实也是对象, 我们可以对其进行retain操作, 在block做为属性的时候我们通常用copy去修饰block, 将block拷贝到堆内存中.
这两个block用于创建SCNetworkReachabilityContext结构体, 下边会讲到.
// SCNetworkReachabilityRef 网络连接引用
@property (readonly, nonatomic, assign) SCNetworkReachabilityRef networkReachability;
// 网络状态, 枚举类型
@property (readwrite, nonatomic, assign) AFNetworkReachabilityStatus networkReachabilityStatus;
// 网络状态切换block
@property (readwrite, nonatomic, copy) AFNetworkReachabilityStatusBlock networkReachabilityStatusBlock;
在.m文件中定义的三个属性.
- (void)startMonitoring {
[self stopMonitoring];
// 句柄
if (!self.networkReachability) {
return;
}
// callback回调
__weak __typeof(self)weakSelf = self;
AFNetworkReachabilityStatusBlock callback = ^(AFNetworkReachabilityStatus status) {
__strong __typeof(weakSelf)strongSelf = weakSelf;
strongSelf.networkReachabilityStatus = status;
if (strongSelf.networkReachabilityStatusBlock) {
strongSelf.networkReachabilityStatusBlock(status);
}
};
/**
typedef struct {
CFIndex version;
void * __nullable info;// void * 相当于oc中的id类型, 可以指向任何类型的参数
const void * __nonnull (* __nullable retain)(const void *info);// 接收一个函数, 目的是对info做retain操作
void (* __nullable release)(const void *info);// 接收一个函数, 目的是对info做release操作
CFStringRef __nonnull (* __nullable copyDescription)(const void *info);// 接收一个函数, 根据info获取description字符串
} SCNetworkReachabilityContext;
context是一个结构体
*/
SCNetworkReachabilityContext context = {0, (__bridge void *)callback, AFNetworkReachabilityRetainCallback, AFNetworkReachabilityReleaseCallback, NULL};
// 根据上下文设置回调
SCNetworkReachabilitySetCallback(self.networkReachability, AFNetworkReachabilityCallback, &context);
// 加入线程池中 mainRunLoop commonModes
SCNetworkReachabilityScheduleWithRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0),^{
SCNetworkReachabilityFlags flags;
if (SCNetworkReachabilityGetFlags(self.networkReachability, &flags)) {
AFPostReachabilityStatusChange(flags, callback);
}
});
}
这个是主要讲解的方法, AFNetworkReachabilityManager监测网络状态的核心就在此方法.
SCNetworkReachabilityContext是一个结构体(个人理解为结构体主要用于存储数据), void * __nullable info是指向需要执行的block的指针, 包含了用户指定的数据和用于SCNetworkReachabilitySetCallback方法的回调函数.
SCNetworkReachabilitySetCallback设置回调, 可以看我的另一篇文章有简要介绍.
SCNetworkReachabilityScheduleWithRunLoop将networkReachability网络连接引用加入到运行循环中. 个人理解为加入运行循环以后会一直监测networkReachability网络状态, 如果网络状态有变化就会调用AFNetworkReachabilityCallback.
在异步线程中发送一次网络状态, 调用SCNetworkReachabilityGetFlags获取网络状态, AFPostReachabilityStatusChange发送网路状态.
- (void)stopMonitoring {
if (!self.networkReachability) {
return;
}
SCNetworkReachabilityUnscheduleFromRunLoop(self.networkReachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
}
从指定的运行循环和模式中移除网络连接引用的调度. 也就是说不再监听networkReachability的网络状态.
#pragma mark - NSKeyValueObserving
+ (NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key {
if ([key isEqualToString:@"reachable"] || [key isEqualToString:@"reachableViaWWAN"] || [key isEqualToString:@"reachableViaWiFi"]) {
return [NSSet setWithObject:@"networkReachabilityStatus"];
}
return [super keyPathsForValuesAffectingValueForKey:key];
}
键值依赖, 返回一个键集合, 这些属性的值会影响指定的key的值, 当集合中键的值发生变化时, 就会触发指定key的监听通知.
当networkReachabilityStatus的值发生变化时, 就会触发指定的key的键值监听方法.
利用一天的时间整理了一下, 如果有错误的地方, 希望能够指出, 共同进步.