我花了一天半的大部分时间来尝试调试此问题，当我尝试取消存档本地存储的数据blob时（通过iCloud检索该问题时也会出现此问题，但是由于它们贯穿相同的代码路径，我认为它们是相关的。
背景
我最初是在四年前构建此应用程序的，但由于其后一直不知所措（但可能是因为那时我还是一个新手，所以我依靠AutoCoding库在我的数据模型中获取对象）自动采用NSCoding（尽管我确实在某些地方自己实现了该协议-就像我说的，我是新手）和FCFileManager将这些对象保存到本地文档目录中。数据模型本身非常简单：具有NSString，NSArray和其他自定义NSObject类的各种属性的自定义NSObject（但我会注意到有许多循环引用；大多数在头文件中声明为强且非原子的）。这种组合在应用的正式版中具有（并且仍然可以）正常运行。
但是，在以后的更新中，我计划从iCloud添加保存/加载文件。在进行扩展时，我一直在寻找减少第三方依赖项列表并将旧代码更新为iOS 13+ API的方法。碰巧，FCFileManager依赖于现在不推荐使用的+[NSKeyedUnarchiver unarchiveObjectWithFile:]和+[NSKeyedArchiver archiveRootObject:toFile:]，所以我一直专注于使用更现代的API从该库重写我需要的内容。
我可以使用以下命令轻松保存文件：
@objc static func save(_ content: NSCoding, at fileName: String, completion: ((Bool, Error?) -> ())?) {
CFCSerialQueue.processingQueue.async { // my own serial queue
measureTime(operation: "[LocalService Save] Saving") { // just measures the time it takes for the logic in the closure to process
do {
let data: Data = try NSKeyedArchiver.archivedData(withRootObject: content, requiringSecureCoding: false)
// targetDirectory here is defined earlier in the class as the local documents directory
try data.write(to: targetDirectory!.appendingPathComponent(fileName), options: .atomicWrite)
if (completion != nil) {
completion!(true, nil)
}
} catch {
if (completion != nil) {
completion!(false, error)
}
}
}
}
}
而且效果很好-非常快，并且仍可以由FCFileManager的+[NSKeyedUnarchiver unarchiveObjectWithFile:]最小包装程序加载。
问题
但是从本地文档目录加载该文件back已证明是一个巨大的挑战。这是我现在正在使用的内容：
@objc static func load(_ fileName: String, completion: @escaping ((Any?, Error?) -> ())) {
CFCSerialQueue.processingQueue.async {// my own serial queue
measureTime(operation: "[LocalService Load] Loading") {
do {
// targetDirectory here is defined earlier in the class as the local documents directory
let combinedUrl: URL = targetDirectory!.appendingPathComponent(fileName)
if (FileManager.default.fileExists(atPath: combinedUrl.path)) {
let data: Data = try Data(contentsOf: combinedUrl)
let obj: Any? = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data)
completion(obj, nil)
} else {
completion(nil, ServiceError.generic(message: "Data not found at URL \(combinedUrl)"))
}
} catch {
completion(nil, error)
}
}
}
}
我已经用新的+[NSKeyedUnarchiver unarchiveObjectWithFile:]替换了FCFileManager的+[NSKeyedUnarchiver unarchiveTopLevelObjectWithData:]，但是当执行流经该行时，我遇到了EXC_BAD_ACCESS code = 2崩溃。 stacktrace从来没有特别有用。通常长约1500帧，并在各种自定义-[NSObject initWithCoder:]实现之间跳转。这是一个示例（添加了有关上下文，清晰和简洁的注释）：
@implementation Game
@synthesize AwayKStats,AwayQBStats,AwayRB1Stats,AwayRB2Stats,AwayWR1Stats,AwayWR2Stats,AwayWR3Stats,awayTOs,awayTeam,awayScore,awayYards,awayQScore,awayStarters,gameName,homeTeam,hasPlayed,homeYards,HomeKStats,superclass,HomeQBStats,HomeRB1Stats,HomeRB2Stats,homeStarters,HomeWR1Stats,HomeWR2Stats,HomeWR3Stats,homeScore,homeQScore,homeTOs,numOT,AwayTEStats,HomeTEStats, gameEventLog,HomeSStats,HomeCB1Stats,HomeCB2Stats,HomeCB3Stats,HomeDL1Stats,HomeDL2Stats,HomeDL3Stats,HomeDL4Stats,HomeLB1Stats,HomeLB2Stats,HomeLB3Stats,AwaySStats,AwayCB1Stats,AwayCB2Stats,AwayCB3Stats,AwayDL1Stats,AwayDL2Stats,AwayDL3Stats,AwayDL4Stats,AwayLB1Stats,AwayLB2Stats,AwayLB3Stats,homePlays,awayPlays,playEffectiveness, homeStarterSet, awayStarterSet;
-(id)initWithCoder:(NSCoder *)aDecoder {
self = [super init];
if (self) {
// ...lots of other decoding...
// stack trace says the BAD_ACCESS is flowing through these decoding lines
// @property (atomic) Team *homeTeam;
homeTeam = [aDecoder decodeObjectOfClass:[Team class] forKey:@"homeTeam"];
// @property (atomic) Team *awayTeam;
// there's no special reason for this line using a different decoding method;
// I was just trying to test out both
awayTeam = [aDecoder decodeObjectForKey:@"awayTeam"];
// ...lots of other decoding...
}
return self;
}
每个游戏对象都有一个主队和客队；每个团队都有一个NSMutableArray游戏对象，称为gameSchedule，定义如下：
@property (strong, atomic) NSMutableArray<Game*> *gameSchedule;
这里是团队的initWithCoder：实现：
-(id)initWithCoder:(NSCoder *)coder {
self = [super initWithCoder:coder];
if (self) {
if (teamHistory.count > 0) {
if (teamHistoryDictionary == nil) {
teamHistoryDictionary = [NSMutableDictionary dictionary];
}
if (teamHistoryDictionary.count < teamHistory.count) {
for (int i = 0; i < teamHistory.count; i++) {
[teamHistoryDictionary setObject:teamHistory[i] forKey:[NSString stringWithFormat:@"%ld",(long)([HBSharedUtils currentLeague].baseYear + i)]];
}
}
}
if (state == nil) {
// set the home state here
}
if (playersTransferring == nil) {
playersTransferring = [NSMutableArray array];
}
if (![coder containsValueForKey:@"projectedPollScore"]) {
if (teamOLs != nil && teamQBs != nil && teamRBs != nil && teamWRs != nil && teamTEs != nil) {
FCLog(@"[Team Attributes] Adding Projected Poll Score to %@", self.abbreviation);
projectedPollScore = [self projectPollScore];
} else {
projectedPollScore = 0;
}
}
if (![coder containsValueForKey:@"teamStrengthOfLosses"]) {
[self updateStrengthOfLosses];
}
if (![coder containsValueForKey:@"teamStrengthOfSchedule"]) {
[self updateStrengthOfSchedule];
}
if (![coder containsValueForKey:@"teamStrengthOfWins"]) {
[self updateStrengthOfWins];
}
}
return self;
}
非常简单，除了回填某些属性外。但是，此类会导入AutoCoding，它会像下面这样钩接到-[NSObject initWithCoder:]中：
- (void)setWithCoder:(NSCoder *)aDecoder
{
BOOL secureAvailable = [aDecoder respondsToSelector:@selector(decodeObjectOfClass:forKey:)];
BOOL secureSupported = [[self class] supportsSecureCoding];
NSDictionary *properties = self.codableProperties;
for (NSString *key in properties)
{
id object = nil;
Class propertyClass = properties[key];
if (secureAvailable)
{
object = [aDecoder decodeObjectOfClass:propertyClass forKey:key]; // where the EXC_BAD_ACCESS seems to be coming from
}
else
{
object = [aDecoder decodeObjectForKey:key];
}
if (object)
{
if (secureSupported && ![object isKindOfClass:propertyClass] && object != [NSNull null])
{
[NSException raise:AutocodingException format:@"Expected '%@' to be a %@, but was actually a %@", key, propertyClass, [object class]];
}
[self setValue:object forKey:key];
}
}
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
[self setWithCoder:aDecoder];
return self;
}
我进行了一些代码跟踪，发现执行过程在上面的-[NSCoder decodeObject:forKey:]调用中进行。基于我添加的一些日志，似乎propertyClass在传递给-[NSCoder decodeObjectOfClass:forKey:]之前已经以某种方式被释放了。但是，Xcode显示崩溃发生时propertyClass具有一个值（请参见屏幕截图：https://imgur.com/a/J0mgrvQ）
在该框架中定义的属性：
@property (strong, nonatomic) Record *careerFgMadeRecord;
并且本身具有以下属性：
@interface Record : NSObject
@property (strong, nonatomic) NSString *title;
@property (nonatomic) NSInteger year;
@property (nonatomic) NSInteger statistic;
@property (nonatomic) Player *holder;
@property (nonatomic) HeadCoach *coachHolder;
// … some functions
@end
此类也导入AutoCoding，但没有自定义initWithCoder：或setWithCoder：实现。
[奇怪的是，用FCFileManager版本替换我编写的加载方法也会崩溃，因此，如何存储数据而不是如何获取数据可能是更多问题。但是同样，在使用FCFileManager的方法加载/保存文件时，这一切都可以正常工作，因此我的猜测是，iOS 11（上次更新FCFileManager时）和iOS 12+（当NSKeyedArchiver API已更新）。
根据我在网上找到的一些建议（例如该建议），我也尝试过此方法：
@objc static func load(_ fileName: String, completion: @escaping ((Any?, Error?) -> ())) {
CFCSerialQueue.processingQueue.async {
measureTime(operation: "[LocalService Load] Loading") {
do {
let combinedUrl: URL = targetDirectory!.appendingPathComponent(fileName)
if (FileManager.default.fileExists(atPath: combinedUrl.path)) {
let data: Data = try Data(contentsOf: combinedUrl)
let unarchiver: NSKeyedUnarchiver = try NSKeyedUnarchiver(forReadingFrom: data)
unarchiver.requiresSecureCoding = false;
let obj: Any? = try unarchiver.decodeTopLevelObject(forKey: NSKeyedArchiveRootObjectKey)
completion(obj, nil)
} else {
completion(nil, ServiceError.generic(message: "Data not found at URL \(combinedUrl)"))
}
} catch {
completion(nil, error)
}
}
}
}
但是，在尝试解码时，它仍然抛出相同的EXC_BAD_ACCESS。
有人对我可能在这里出问题的地方有任何见识吗？我敢肯定这很简单，但似乎无法弄清楚。如果需要更深入地研究，我可以提供更多源代码。
感谢您的帮助！
我（以某种方式）通过依靠AutoCoding来管理Game类的NSCoding实现来克服了这一点。剥离图层，似乎在-[NSMutableArray arrayWithObjects:]中使用-[Game initWithCoder:]会导致EXC_BAD_ACCESS出现一些问题，但是当退回到AutoCoding时，这种问题似乎也消失了。不知道这会对向后兼容性产生什么影响，但是我想到达那儿后我会越过那座桥梁。