监听手机通讯录的变化减少每次进入程序重新获取通讯录信息。主要使用了AddressBook和CNContact来完成
有两种实现方式：
1.使用框架AddressBook

//监听通讯录变化
void addressBookChanged(ABAddressBookRef addressBook, CFDictionaryRef info, void *context)
{
    NSLog(@"AddressBook Changed");
//    VC1 *myVC = (__bridge VC1 *)context;
//    [myVC getPersonOutOfAddressBook];
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
    
    ABAddressBookRef addresBook = ABAddressBookCreateWithOptions(NULL, NULL);
    ABAddressBookRegisterExternalChangeCallback(addresBook, addressBookChanged, (__bridge void *)(self.viewcontrller));
}
    ```
调用此方法需要放在-application:didFinishLaunchingWithOptions:
2.使用CNContact框架，
**Obj-C code:**

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(addressBookDidChange:) name:CNContactStoreDidChangeNotification object:nil];

然后

-(void)addressBookDidChange:(NSNotification*)notification{

}

**Swift code:**

NSNotificationCenter.defaultCenter().addObserver( self, selector: "addressBookDidChange:", name: CNContactStoreDidChangeNotification, object: nil)

然后

@objc func addressBookDidChange(notification: NSNotification){
}