使用KVO模式,设置应用角标数字

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //注册推送
    //申请设置角标数字权限
    [application registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil]];
    
    return YES;
}
//观察者回调方法
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context
{
    //获取badgeValue的新值
    NSString *value = change[NSKeyValueChangeNewKey];
    NSLog(@"%@",value);
    [UIApplication sharedApplication].applicationIconBadgeNumber = value.integerValue ;
}

#import "ViewController.h"
#import "AppDelegate.h"
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    
    AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
    //注册观察者
    [self addObserver:appDelegate forKeyPath:@"tabBarItem.badgeValue" options:NSKeyValueObservingOptionNew context:nil];
    //触发观察者
    self.tabBarItem.badgeValue = @"9";
    self.tabBarItem.badgeValue = @"123";
    self.tabBarItem.badgeValue = @"456";
    //移除观察者
    [self removeObserver:appDelegate forKeyPath:@"tabBarItem.badgeValue"];
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}