最近在做一個(gè)關(guān)于UNUserNotification通知的需求叛复，需要獲取當(dāng)前APP的通知權(quán)限仔引，由于iOS10以上通知使用的API發(fā)生了很大的變化扔仓，在iOS 10以下獲取通知設(shè)置(notification settings)代碼如下：

 UIUserNotificationSettings *theSettings = [[UIApplication sharedApplication] currentUserNotificationSettings];
return [theSettings types] & UIUserNotificationTypeAlert;

?而 iOS10采用UNUserNotificationCenter代替了原有的API。使用UNUserNotificationCenter獲取APP通知設(shè)置代碼如下：

   UNUserNotificationCenter *notificationCenter=[UNUserNotificationCenter currentNotificationCenter];
        [notificationCenter getNotificationSettingsWithCompletionHandler:^(UNNotificationSettings * _Nonnull settings) {
            switch (settings.authorizationStatus) {
                case UNAuthorizationStatusAuthorized:
                    enabled = YES;
                    break;
                default:
                    break;
            }
        }];

getNotificationSettingsWithCompletionHandler:采用的是異步回調(diào)的過程咖耘。為了寫一個(gè)兼容兩種類型的函數(shù)翘簇，我的代碼如下：

   __block BOOL enabled = NO;
    if (@available(iOS 10.0, *)) {
        UNUserNotificationCenter *notificationCenter=[UNUserNotificationCenter currentNotificationCenter];
        [notificationCenter getNotificationSettingsWithCompletionHandler:^(UNNotificationSettings * _Nonnull settings) {
            switch (settings.authorizationStatus) {
                case UNAuthorizationStatusAuthorized:
                    enabled = YES;
                    break;
                default:
                    break;
            }
        }];
    } else {
       UIApplication *application = [UIApplication sharedApplication];
        if ([application respondsToSelector:@selector(isRegisteredForRemoteNotifications)]) {
            UIUserNotificationSettings *settings = [application currentUserNotificationSettings];
            if (settings.types != UIUserNotificationTypeNone) {
                enabled = YES;
            }
        }
    }

這樣貌似很完美，其實(shí)這段代碼犯了一個(gè)很低級(jí)的錯(cuò)誤鲤看。把異步當(dāng)成同步再用缘揪。當(dāng)時(shí)發(fā)現(xiàn)這個(gè)問題時(shí)，APP已經(jīng)上線了义桂，最后只好向領(lǐng)導(dǎo)老實(shí)認(rèn)錯(cuò)寫檢討找筝。傷心太平洋(πーπ)

出現(xiàn)錯(cuò)誤肯定要改嘛，最后想到了用信號(hào)量來強(qiáng)制將異步變?yōu)橥娇兜酰暮蟮拇a如下：

  __block BOOL enabled = NO;
    if (@available(iOS 10.0, *)) {
        dispatch_semaphore_t sem;
        sem = dispatch_semaphore_create(0);
        UNUserNotificationCenter *notificationCenter=[UNUserNotificationCenter currentNotificationCenter];
        [notificationCenter getNotificationSettingsWithCompletionHandler:^(UNNotificationSettings * _Nonnull settings) {
            switch (settings.authorizationStatus) {
                case UNAuthorizationStatusAuthorized:
                    enabled = YES;
                    break;
                default:
                    break;
            }
            dispatch_semaphore_signal(sem);
        }];
        dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER); //獲取通知設(shè)置的過程是異步的袖裕，這里需要等待
    } else {
          UIApplication *application = [UIApplication sharedApplication];
        if ([application respondsToSelector:@selector(isRegisteredForRemoteNotifications)]) {
            UIUserNotificationSettings *settings = [application currentUserNotificationSettings];
            if (settings.types != UIUserNotificationTypeNone) {
                enabled = YES;
            }
        }
    } 

另附上Stack Overflow一個(gè)獲取Notification Settings通用的類，
地址
.h文件

#import <UIKit/UIKit.h>

typedef NS_ENUM(NSInteger , PushNotificationType) {
    PushNotificationTypeNone    = 0,      // the application may not present any UI upon a notification being received
    PushNotificationTypeBadge   = 1 << 0, // the application may badge its icon upon a notification being received
    PushNotificationTypeSound   = 1 << 1, // the application may play a sound upon a notification being received
    PushNotificationTypeAlert   = 1 << 2, // the application may display an alert upon a notification being received
};

@interface SpecificPush : NSObject

@property (nonatomic, readonly) PushNotificationType currentNotificationSettings;

+ (SpecificPush *)sharedInstance;
- (PushNotificationType)types;

@end

.m文件

#import <UserNotifications/UserNotifications.h>

@interface SpecificPush()
@property (nonatomic) PushNotificationType currentNotificationSettings;
@end

@implementation SpecificPush

#pragma mark - Init

static SpecificPush *instance = nil;
+ (SpecificPush *)sharedInstance
{
    @synchronized (self)
    {
        if (instance == nil)
        {
            [SpecificPush new];
        }
    }
    return instance;
}

- (instancetype)init
{
    NSAssert(!instance, @"WARNING - Instance of SpecifishPush already exists");
    self = [super init];
    if (self)
    {
        self.currentNotificationSettings = PushNotificationTypeNone;
    }
    instance = self;
    return self;
}

- (PushNotificationType)types
{
    if (@available(iOS 10.0, *))
    {
        dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

        [[UNUserNotificationCenter currentNotificationCenter] getNotificationSettingsWithCompletionHandler:^(UNNotificationSettings *settings) {
            if ((settings.soundSetting == UNNotificationSettingDisabled) && (settings.alertSetting == UNNotificationSettingDisabled) && (settings.soundSetting == UNNotificationSettingDisabled))
            {
                self.currentNotificationSettings = PushNotificationTypeNone;
            }
            if (settings.badgeSetting == UNNotificationSettingEnabled)
            {
                self.currentNotificationSettings = PushNotificationTypeBadge;
            }
            if (settings.soundSetting == UNNotificationSettingEnabled)
            {
                self.currentNotificationSettings = PushNotificationTypeSound;
            }

            if (settings.alertStyle == UNNotificationSettingEnabled)
            {
                self.currentNotificationSettings = PushNotificationTypeAlert;
            }

            dispatch_semaphore_signal(semaphore);

        }];

        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
        dispatch_release(semaphore);
    }
    else
    {
        UIUserNotificationSettings *settings = [[UIApplication sharedApplication] currentUserNotificationSettings];

        if (settings.types == UIUserNotificationTypeNone)
        {
            self.currentNotificationSettings = PushNotificationTypeNone;
        }
        if (settings.types & UIUserNotificationTypeBadge)
        {
            self.currentNotificationSettings = PushNotificationTypeBadge;
        }
        if (settings.types & UIUserNotificationTypeSound)
        {
            self.currentNotificationSettings = PushNotificationTypeSound;
        }
        if (settings.types & UIUserNotificationTypeAlert)
        {
            self.currentNotificationSettings = PushNotificationTypeAlert;
        }
    }

    return self.currentNotificationSettings;
}
@end