出身背景
在我的应用程序中,我有一个名为FavoritesController的类,它管理用户标记为收藏夹的对象,然后在整个应用程序中使用此收藏夹状态。FavoritesController设计为一个单例类,因为整个应用程序中有许多UI元素需要知道不同位置对象的“收藏夹状态”,而且如果服务器这样说,网络请求需要能够发出收藏夹需要失效的信号。
当服务器响应404错误时,会发生此无效部分,指示必须从用户的收藏夹中删除收藏夹对象。network fetch函数引发错误,这会触发FavoritesController删除对象,然后向相关方发送需要刷新的通知。
问题所在
当使用单元测试检查404实现的质量时,所有方法都会按预期触发–抛出并捕获错误,FavoritesController删除对象并发送通知。但在某些情况下,删除的收藏夹仍然存在,但这取决于查询的位置!
如果我在单例中进行查询,则删除操作正常,但如果我从使用单例的类中进行查询,则不会发生删除操作。
设计细节
-
FavoritesController属性
favorites
对所有访问使用ivar
@synchronized()
,并且ivar的值由NSUserDefaults属性支持。
-
收藏夹对象是具有两个键的NSDictionary:
id
和
name
。
其他信息
-
有一件奇怪的事情我不明白为什么会发生:在一些删除尝试中
名称
收藏夹对象的值设置为
""
但是
身份证件
键保留其值。
-
我编写了单元测试,添加一个无效的收藏夹,并检查它是否在第一次服务器查询时被删除。当从一组空收藏夹开始时,此测试通过,但当存在如上所述的“半删除”对象的实例(保留其
身份证件
值)
-
单元测试现在一直通过,但在实际使用中,删除失败仍然存在。我怀疑这是由于NSUserDefaults没有立即保存到磁盘。
我试过的步骤
-
确保singleton实现是“真正的”singleton,即。
sharedController
始终返回相同的实例。
-
我原以为存在某种“捕获”问题,即闭包会将自己的副本保存在过时的收藏夹中,但我认为不是这样。在记录对象ID时,它会返回相同的ID。
密码
FavoritesController主要方法
- (void) serverCanNotFindFavorite:(NSInteger)siteID {
NSLog(@"Server can't find favorite");
NSDictionary * removedFavorite = [NSDictionary dictionaryWithDictionary:[self favoriteWithID:siteID]];
NSUInteger index = [self indexOfFavoriteWithID:siteID];
[self debugLogFavorites];
dispatch_async(dispatch_get_main_queue(), ^{
[self removeFromFavorites:siteID completion:^(BOOL success) {
if (success) {
NSNotification * note = [NSNotification notificationWithName:didRemoveFavoriteNotification object:nil userInfo:@{@"site" : removedFavorite, @"index" : [NSNumber numberWithUnsignedInteger:index]}];
NSLog(@"Will post notification");
[self debugLogFavorites];
[self debugLogUserDefaultsFavorites];
[[NSNotificationCenter defaultCenter] postNotification:note];
NSLog(@"Posted notification with name: %@", didRemoveFavoriteNotification);
}
}];
});
}
- (void) removeFromFavorites:(NSInteger)siteID completion:(completionBlock) completion {
if ([self isFavorite:siteID]) {
NSMutableArray * newFavorites = [NSMutableArray arrayWithArray:self.favorites];
NSIndexSet * indices = [newFavorites indexesOfObjectsPassingTest:^BOOL(NSDictionary * entryUnderTest, NSUInteger idx, BOOL * _Nonnull stop) {
NSNumber * value = (NSNumber *)[entryUnderTest objectForKey:@"id"];
if ([value isEqualToNumber:[NSNumber numberWithInteger:siteID]]) {
return YES;
}
return NO;
}];
__block NSDictionary* objectToRemove = [[newFavorites objectAtIndex:indices.firstIndex] copy];
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"Will remove %@", objectToRemove);
[newFavorites removeObject:objectToRemove];
[self setFavorites:[NSArray arrayWithArray:newFavorites]];
if ([self isFavorite:siteID]) {
NSLog(@"Failed to remove!");
if (completion) {
completion(NO);
}
} else {
NSLog(@"Removed OK");
if (completion) {
completion(YES);
}
}
});
} else {
NSLog(@"Tried removing site %li which is not a favorite", (long)siteID);
if (completion) {
completion(NO);
}
}
}
- (NSArray *) favorites
{
@synchronized(self) {
if (!internalFavorites) {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
self->internalFavorites = [self.defaults objectForKey:k_key_favorites];
});
if (!internalFavorites) {
internalFavorites = [NSArray array];
}
}
return internalFavorites;
}
}
- (void) setFavorites:(NSArray *)someFavorites {
@synchronized(self) {
internalFavorites = someFavorites;
[self.defaults setObject:internalFavorites forKey:k_key_favorites];
}
}
- (void) addToFavorites:(NSInteger)siteID withName:(NSString *)siteName {
if (![self isFavorite:siteID]) {
NSDictionary * newFavorite = @{
@"name" : siteName,
@"id" : [NSNumber numberWithInteger:siteID]
};
dispatch_async(dispatch_get_main_queue(), ^{
NSArray * newFavorites = [self.favorites arrayByAddingObject:newFavorite];
[self setFavorites:newFavorites];
});
NSLog(@"Added site %@ with id %ld to favorites", siteName, (long)siteID);
} else {
NSLog(@"Tried adding site as favorite a second time");
}
}
- (BOOL) isFavorite:(NSInteger)siteID
{
@synchronized(self) {
NSNumber * siteNumber = [NSNumber numberWithInteger:siteID];
NSArray * favs = [NSArray arrayWithArray:self.favorites];
if (favs.count == 0) {
NSLog(@"No favorites");
return NO;
}
NSIndexSet * indices = [favs indexesOfObjectsPassingTest:^BOOL(NSDictionary * entryUnderTest, NSUInteger idx, BOOL * _Nonnull stop) {
if ([[entryUnderTest objectForKey:@"id"] isEqualToNumber:siteNumber]) {
return YES;
}
return NO;
}];
if (indices.count > 0) {
return YES;
}
}
return NO;
}
FavoritesController的单例实现
- (instancetype) init {
static PKEFavoritesController *initedObject;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
initedObject = [super init];
self.defaults = [NSUserDefaults standardUserDefaults];
});
return initedObject;
}
+ (instancetype) sharedController
{
return [self new];
}
单元测试代码
func testObsoleteFavoriteRemoval() {
let addToFavorites = self.expectation(description: "addToFavorites")
let networkRequest = self.expectation(description: "network request")
unowned let favs = PKEFavoritesController.shared()
favs.clearFavorites()
XCTAssertFalse(favs.isFavorite(313), "Should not be favorite initially")
if !favs.isFavorite(313) {
NSLog("Adding 313 to favorites")
favs.add(toFavorites: 313, withName: "Skatås")
}
let notification = self.expectation(forNotification: NSNotification.Name("didRemoveFavoriteNotification"), object: nil) { (notification) -> Bool in
NSLog("Received notification: \(notification.name.rawValue)")
return true
}
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
NSLog("Verifying 313 is favorite")
XCTAssertTrue(favs.isFavorite(313))
addToFavorites.fulfill()
}
self.wait(for: [addToFavorites], timeout: 5)
NSLog("Will trigger removal for 313")
let _ = SkidsparAPI.fetchRecentReports(forSite: 313, session: SkidsparAPI.session()) { (reports) in
NSLog("Network request completed")
networkRequest.fulfill()
}
self.wait(for: [networkRequest, notification], timeout: 10)
XCTAssertFalse(favs.isFavorite(313), "Favorite should be removed after a 404 error from server")
}
