监控网络状态的改变

为了程序的安全性，在进行网络请求时，有必要判断网络连通性，有时也需要根据当前没有网/是wwan或wifi做不同的操作。

首先添加框架SystemConfiguration.framework，然后导入Reachability.h和Reachability.m。

（下载地址：http://download.csdn.net/download/yiran_style/4979061）

之后，可以对这两个库进行封装，下面记下我的个人封装：

ReachabilityChecker.h：

#import <Foundation/Foundation.h>
#import "Reachability.h"

typedef void (^ActionBlock)();

@class Reachability;

@interface BBBReachabilityChecker : NSObject

@property (retain, nonatomic) Reachability *hostReach;

//回调事件
@property (copy, nonatomic, readonly) ActionBlock notReachableEventBlock;
@property (copy, nonatomic, readonly) ActionBlock reachableViaWiFiEventBlock;
@property (copy, nonatomic, readonly) ActionBlock reachableViaWWANEventBlock;

//当前网络状态
@property (assign, nonatomic, readonly) NetworkStatus currentNetworkStatus;

//单例
+ (BBBReachabilityChecker *)sharedInstance;

//开启网络状态监听循环
- (void)beginListenerRunLoopAtAppDelegate:(id<UIApplicationDelegate>) appDelegate;

//注册断网、切换到WWAN或WiFi时的事件
- (void)registOnStatusChangeToNotReachableEvent:(ActionBlock)block;
- (void)registOnStatusChangeToReachableViaWiFiEvent:(ActionBlock)block;
- (void)registOnStatusChangeToReachableViaWWANEvent:(ActionBlock)block;

@end

ReachabilityChecker.m:

#import "ReachabilityChecker.h"
#import "Reachability.h"

static ReachabilityChecker *_sharedInstance = nil;

@implementation ReachabilityChecker

#pragma mark - 单例构造
+ (BBBReachabilityChecker *)sharedInstance {
    if (_sharedInstance == nil) {
        @synchronized(self) {
            _sharedInstance = [[super allocWithZone:nil] init];
        }
    }
    return _sharedInstance;
}

+(id)allocWithZone:(struct _NSZone *)zone {
    return [[self sharedInstance] retain];
}

-(id)copyWithZone:(NSZone *)zone {
    return self;
}

-(id)init {
    if (_sharedInstance) {
        return _sharedInstance;
    }
    self = [super init];
    return self;
}

- (id)retain {
    return self;
}

- (oneway void)release {
    // Do nothing
}

-(id)autorelease {
    return self;
}

-(NSUInteger)retainCount {
    return NSUIntegerMax;
}

#pragma mark - 公有方法实现

//开启网络状态监听循环
- (void)beginListenerRunLoopAtAppDelegate:(__weak id<UIApplicationDelegate>) appDelegate {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(pReachabilityChanged:) name: kReachabilityChangedNotification object: nil];
    self.hostReach = [Reachability reachabilityWithHostName:@"www.baidu.com"];
    [self.hostReach startNotifier];
}

#pragma mark - 私有方法实现

//响应通知中心
- (void)pReachabilityChanged:(NSNotification *)note
{
    Reachability *curReach = [note object];
    [self pUpdateInterfaceWithReachability: curReach];
}

//处理连接改变后的情况
- (void)pUpdateInterfaceWithReachability: (Reachability*) curReach
{
    NetworkStatus status = [curReach currentReachabilityStatus];
    
    //记录网络状态
    _currentNetworkStatus = status;
    
    if (status == NotReachable) {
        if (_notReachableEventBlock != NULL) {
            _notReachableEventBlock();
        }
    }
    else if (status == ReachableViaWiFi) {
        if (_reachableViaWiFiEventBlock != NULL) {
            _reachableViaWiFiEventBlock();
        }
    }
    else if (status == ReachableViaWWAN) {
        if (_reachableViaWWANEventBlock != NULL) {
            _reachableViaWWANEventBlock();
        }
    }
}

#pragma mark - 注册断网、切换到WiFi/WWAN时的事件
- (void)registOnStatusChangeToNotReachableEvent:(ActionBlock)block {
    if (_notReachableEventBlock != NULL) {
        Block_release(_notReachableEventBlock);
    }
    _notReachableEventBlock = [block copy];
}

- (void)registOnStatusChangeToReachableViaWiFiEvent:(ActionBlock)block {
    if (_reachableViaWiFiEventBlock != NULL) {
        Block_release(_reachableViaWiFiEventBlock);
    }
    _reachableViaWiFiEventBlock = [block copy];
}

- (void)registOnStatusChangeToReachableViaWWANEvent:(ActionBlock)block {
    if (_reachableViaWWANEventBlock != NULL) {
        Block_release(_reachableViaWWANEventBlock);
    }
    _reachableViaWWANEventBlock = [block copy];
}

@end

接下来只要在应用程序代理当中初始化这个类即可：

    //开启网络状态监听
    [[BBBReachabilityChecker sharedInstance] beginListenerRunLoopAtAppDelegate:self];

然后可以设置三个block来处理网络状态发生变化时的事件（当然，应该也可以利用target-action的形式进行封装），此外，这个封装还可以直接取到当前网络状态的枚举值。