Question

我正在预加载一个sqlite数据库，然后将其与用于创建sqlite数据库的完全相同的数据模型捆绑到另一个项目中。我的managedObjectContext的代码：

lazy var managedObjectContext: NSManagedObjectContext = {
        guard let modelURL = Bundle.main.url(forResource: "DataModel", withExtension: "momd") else {
            fatalError("Error getting data model url from the main bundle!")
        }
        guard let model = NSManagedObjectModel(contentsOf: modelURL) else {
            fatalError("Error initiating the data model!")
        }
        let urls = FileManager.default.urls(for: FileManager.SearchPathDirectory.documentDirectory, in: FileManager.SearchPathDomainMask.userDomainMask)
        var documentsDirectory = urls[0]
        let dataStoreURL = documentsDirectory.appendingPathComponent("DataStore.sqlite")
        do {
            try FileManager.default.copyItem(at: Bundle.main.url(forResource: "DataStore", withExtension: "sqlite")!, to: documentsDirectory.appendingPathComponent("DataStore.sqlite"))
            try FileManager.default.copyItem(at: Bundle.main.url(forResource: "DataStore", withExtension: "sqlite-shm")!, to: documentsDirectory.appendingPathComponent("DataStore.sqlite-shm"))
            try FileManager.default.copyItem(at: Bundle.main.url(forResource: "DataStore", withExtension: "sqlite-wal")!, to: documentsDirectory.appendingPathComponent("DataStore.sqlite-wal"))
        } catch let error as NSError {
            fatalError(error.debugDescription)
        }
        do{
            let coordinator = NSPersistentStoreCoordinator(managedObjectModel: model)
            try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: dataStoreURL, options: nil)
            let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
            context.persistentStoreCoordinator = coordinator
            return context
        } catch let error as NSError {
            fatalError("Error adding persistent store at \(dataStoreURL): \(error)")
        }
    }()

当我运行项目时，我收到此错误：

reason=The model used to open the store is incompatible with the one used to create the store

我使用完全相同的数据模型;怎么会不相容？

有人可以帮我理解我做错了吗？

更新：我发现问题，我试图将预装的sqlite数据库复制到文档目录中，即使首先存在一个。我添加了一个条件，如果数据库不存在，只能将数据库从主包复制到第一次运行的文档目录。更新后的代码如下：

lazy var managedObjectContext: NSManagedObjectContext = {
        //**********************Getting Data Model********************************
        guard let dataModelURL = Bundle.main.url(forResource: "DataModel", withExtension: "mom") else {
            fatalError("Failed to get data  model URL from main bundle!")
        }
        guard let dataModel = NSManagedObjectModel(contentsOf: dataModelURL) else {
            fatalError("Failed to initiate data model from the main bundle!")
        }
        //**********************Getting persistence store*************************
        let documentsDirectoryURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
        let dataStoreURL = documentsDirectoryURL.appendingPathComponent("DataStore.sqlite")
        if !FileManager.default.fileExists(atPath: dataStoreURL.path){
            let sourceSqliteURLs = [Bundle.main.url(forResource: "DataStore", withExtension: "sqlite"), Bundle.main.url(forResource: "DataStore", withExtension: "sqlite-shm"), Bundle.main.url(forResource: "DataStore", withExtension: "sqlite-wal")]
            let destSqliteURLs = [documentsDirectoryURL.appendingPathComponent("DataStore.sqlite"), documentsDirectoryURL.appendingPathComponent("DataStore.sqlite-shm"), documentsDirectoryURL.appendingPathComponent("DataStore.sqlite-wal")]
            for (index, sourceURL) in sourceSqliteURLs.enumerated() {
                do{ try FileManager.default.copyItem(at: sourceURL!, to: destSqliteURLs[index])
                }catch{
                    fatalError("Error while copying data store files from main bundle to the documents directory!")
                }
            }
        }
        do{
            let persistenceCordinator = NSPersistentStoreCoordinator(managedObjectModel: dataModel)
            try persistenceCordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: dataStoreURL, options: nil)
            //*******************Initiating managed object context******************
            let context = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
            context.persistentStoreCoordinator = persistenceCordinator
            return context
        }catch let error as NSError{
            print(error.debugDescription)
            fatalError("Error initiating managed object context!")
        }
    }()

如何将预加载的sqlite数据库复制到文档目录中？

0 个答案: