Core Data直读App Bundle只读数据库：同配置容器单库真机崩溃问题

基础场景 #

• 存在两个随App新版本不定期更新的只读SQLite数据库
• 不采用将Bundle内SQLite文件拷贝到Documents目录完成版本更新的方案，直接将持久化容器指向App Bundle路径读取数据库内容
• 运行表现对比：
  • 其中一个数据库全平台运行正常
  • 另一个数据库在模拟器下可正常运行，真机上触发崩溃
  • 两个数据库使用完全一致的持久化容器初始化配置逻辑

实现代码对比 #

无崩溃的持久化容器配置 #

该数据库后续通过FetchedResultsController执行查询操作，配置代码如下：

lazy var strengthPersistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "Favs")
    let sqlFileName: String = kStrengthShortFileName
    let sqlFileExtension: String = "sqlite"
    let fileUrl: URL = Bundle.main.url(forResource: sqlFileName, withExtension: sqlFileExtension)!
    let description = NSPersistentStoreDescription(url: fileUrl)
    description.isReadOnly = true
    container.persistentStoreDescriptions = [description]
    container.loadPersistentStores { _, error in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }
    return container
}()

崩溃的持久化容器配置 #

该数据库后续通过单例封装的上下文执行普通fetch查询，配置逻辑与前者完全一致，代码如下：

lazy var everKeneticPersistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "EverKenetic")
    let sqlFileName: String = kEverKineticFileName
    let sqlFileExtension: String = "sqlite"
    let fileUrl: URL = Bundle.main.url(forResource: sqlFileName, withExtension: sqlFileExtension)!
    let description = NSPersistentStoreDescription(url: fileUrl)
    description.isReadOnly = true
    container.persistentStoreDescriptions = [description]
    container.loadPersistentStores { _, error in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }
    return container
}()

崩溃触发的查询逻辑 #

单例封装的查询代码如下，崩溃位置位于context.fetch(fetchRequest)调用处：

class EverKenetic: NSObject {
    private static var manager: EverKenetic = EverKenetic()
    var everKineticContext: NSManagedObjectContext?

    override init() {
        if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
            let theContext = appDelegate.everKeneticPersistentContainer.viewContext
            everKineticContext = theContext
        }
    }

    class func exerciseInfo(_ everKeneticName: String) -> EverKeneticExercise! {
        let fetchRequest: NSFetchRequest<EverKeneticExercise> = EverKeneticExercise.fetchRequest()
        if let context: NSManagedObjectContext = manager.everKineticContext {
            let entity = NSEntityDescription.entity(forEntityName: "EverKeneticExercise", in: context)
            fetchRequest.entity = entity
            fetchRequest.fetchBatchSize = 2
            let predicate: NSPredicate = NSPredicate(format: "name = %@", everKeneticName)
            fetchRequest.predicate = predicate
            let sortDescriptorRoutine = NSSortDescriptor(key: "name", ascending: false)
            fetchRequest.sortDescriptors = [sortDescriptorRoutine]
            fetchRequest.returnsObjectsAsFaults = false

            var fetch: [EverKeneticExercise]?
            do {
                fetch = try context.fetch(fetchRequest)
            } catch _ as NSError {
                fetch = nil
            }
            if let result = fetch, !result.isEmpty {
                return result[0]
            }
        }
        return nil
    }
}

崩溃详情 #

• 抛出异常类型：未捕获的NSInternalInconsistencyException
• 核心错误信息：Can't create support directory (can't create directory)
• 最终结果：程序因NSException类型异常终止

诉求 #

目前直接读取App Bundle内只读Core Data数据库的可参考实现较少，需要对应问题的排查方向和可落地的实现指导。 #

内容的提问来源于stack exchange，提问作者Greg Robertson