NSInMemoryStoreType类型的核心数据会忽略实体的约束

时间:2019-05-10 12:26:28

标签: ios swift unit-testing core-data

我创建了CoreData堆栈的模拟版本

import Foundation
import CoreData

@testable import Companion

final class MockedDatabaseStackController: DatabaseStackControllerProtocol {

    let batchRequestsAvailable: Bool = false

    private lazy var managedObjectModel = NSManagedObjectModel.mergedModel(from: [Bundle(for: type(of: self))])!

    lazy var persistentContainer: NSPersistentContainer = {
        let description = NSPersistentStoreDescription()
        description.type = NSInMemoryStoreType
        description.shouldAddStoreAsynchronously = false

        let container = NSPersistentContainer(
            name: "database",
            managedObjectModel: managedObjectModel
        )
        container.persistentStoreDescriptions = [description]
        container.loadPersistentStores { description, error in
            // Check if the data store is in memory
            precondition( description.type == NSInMemoryStoreType )

            // Check if creating container wrong
            if let error = error {
                fatalError("Create an in-mem coordinator failed \(error)")
            }
        }

        return container
    }()

    init() {
        NotificationCenter.default
            .addObserver(
                self,
                selector: #selector(didManagedObjectContextSave(notification:)),
                name: .NSManagedObjectContextDidSave,
                object: nil
            )
    }

    @objc
    private func didManagedObjectContextSave(notification: Notification) {
        DispatchQueue.main.async { [weak self] in
            self?.persistentContainer.viewContext.mergeChanges(fromContextDidSave: notification)
        }
    }
}

我正在用它来保存一些对象:

private func executeAndSave<T>(_ executionBlock: @escaping ((NSManagedObjectContext) throws -> T)) -> Single<T> {
    let persistentContainer = stackController.persistentContainer

    return Single.create { observer in
        persistentContainer.performBackgroundTask { context in
            do {
                context.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy

                jsons.forEach {
                    let mo = type.init(context: context)
                    mo.update(withGatewayResponse: $0)
                }
                try context.save()

                DispatchQueue.main.async {
                    observer(.success(result))
                }
            } catch {
                DispatchQueue.main.async {
                    observer(.error(error))
                }
            }
        }

        return Disposables.create()
    }
}

func save(jsons: [JSON], as type: GatewayObjectDeserializableAndSavable.Type) -> Single<Void> {
    if jsons.isEmpty {
        log.info("(\(type)) Nothing to save.")
        return .just(())
    }

    log.info("DatabaseHelper will save \(type)")

    return executeAndSave { context in
        jsons.forEach {
            let mo = type.init(context: context)
            mo.update(withGatewayResponse: $0)
        }
    }
}

// Example of usage:
databaseHelper.save(jsons: jsons, as: Herd.self)

我在数据库模型中创建了约束,例如: enter image description here

但是它不起作用。对象在数据库中重复。 enter image description here

请注意,在我使用此CoreData堆栈的主要目标中,一切正常:

final class DatabaseStackController: DatabaseStackControllerProtocol {

    // singleton
    static let controller = DatabaseStackController()

    private static let kDatabaseName = "database"
    let persistentContainer: NSPersistentContainer = DatabaseStackController.buildDatabaseStack(onComplete: nil)

    let batchRequestsAvailable: Bool = true

    private init() {
        addNSMangedObjectContextObservers()
    }

    private static func buildDatabaseStack(onComplete: (() -> Void)?) -> NSPersistentContainer {
        let container = NSPersistentContainer(name: kDatabaseName)
        container.loadPersistentStores { _, error in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }

            onComplete?()
        }

        return container
    }
}

为什么不起作用? NSInMemoryStoreType是否不支持CoreData的约束?有可能修复它吗?

1 个答案:

答案 0 :(得分:1)

我认为您在Core Data中发现了一个错误:(

我有一个有关Core Data的 Unique Constraint 的小演示项目。我确认它可以按预期运行except for some exceptions,并且始终将所有重复项与SQLite存储合并。然后,我粘贴到您的MockedDatabaseStackController类中,并将其persistentContainer.viewContextNSMergeByPropertyObjectTrumpMergePolicy集一起使用。结果:似乎在第一个 save 操作上合并了第一组重复项,但此后没有合并。然后,除了将存储类型更改为NSInMemoryStoreType之外,我再切换回我的Core Data堆栈。结果:它也无法正常工作,与您的MockedDatabaseStackController一样。

Core Data的SQLite存储基础的SQLite数据库在its SQL中支持 UNIQUE 约束。我希望有人能证明我错了,但是,可悲的是,我怀疑Apple使用SQLite的此功能在Core Data中实现了 Unique Constraint 功能,但未能将事实添加到their documentation中只能用于SQLite存储。

我已将其提交给Apple Bug Reporter:50725935。

对于您的测试,我认为您应该对其进行修改以创建临时的SQLite存储。实际上,Venn图的另一端有一些功能-内存存储支持,SQLite存储支持。在内存中进行测试可能会在测试范围中留下漏洞。