Question

我使用MagicalRecord来处理核心数据。

我有一个名为DatabaseManager的单独类来处理与核心数据相关的任务。我有一个初始化程序接受NSManagedObjectContext对象。

import CoreData
import Foundation
import MagicalRecord
import SwiftyJSON

public class DatabaseManager {

    private let context: NSManagedObjectContext!

    init(context: NSManagedObjectContext) {
        self.context = context
    }

    public func insertReports(data: AnyObject, success: () -> Void, failure: (error: NSError?) -> Void) {
        MagicalRecord.cleanUp()
        MagicalRecord.setupCoreDataStackWithStoreNamed("Records")

        let json = JSON(data)
        if let reports = json.array {
            for reportObj in reports {
                let report = Report.MR_createInContext(context) as Report
                report.id = reportObj["Id"].int
                report.type = reportObj["Type"].string!
            }
            context.MR_saveToPersistentStoreAndWait()
            success()
        }
    }

    private func getReport(id: Int) -> Report {
        let idFilter = NSPredicate(format: "id == %@", NSNumber(integer: id))
        let fetchRequest = Report.MR_requestAllWithPredicate(idFilter, inContext: context)
        return Report.MR_executeFetchRequestAndReturnFirstObject(fetchRequest, inContext: context) as Report
    }
}

我初始化类并调用它的insertReports()方法将一些记录插入到核心数据中。

let context = NSManagedObjectContext.MR_defaultContext()
let dbManager = DatabaseManager(context: context)

getReportsFromAPI({ (data) -> Void in
    dbManager.insertReports(data, success: { () -> Void in
        println("Reports added successfully")
    }, failure: { (error) -> Void in
        println("Error inserting Reports: \(error?.localizedDescription)")
    })
}, failure: { (error) -> Void in
    println("Error getting Reports from API: \(error?.localizedDescription)")
})

但这似乎不起作用。我在控制台中得到以下输出。

2015-03-05 00:39:39.412 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setDefaultContext:](0x104396400) Set Default Context: (null)
2015-03-05 00:39:39.412 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setRootSavingContext:](0x104396400) Set Root Saving Context: (null)
2015-03-05 00:39:39.583 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_contextWithStoreCoordinator:](0x104396400) -> Created Context UNNAMED
2015-03-05 00:39:39.584 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setRootSavingContext:](0x104396400) Set Root Saving Context: <NSManagedObjectContext: 0x7f81b04c6b00>
2015-03-05 00:39:39.584 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_newMainQueueContext](0x104396400) Created Main Queue Context: <NSManagedObjectContext: 0x7f81b04c75a0>
2015-03-05 00:39:39.584 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setDefaultContext:](0x104396400) Set Default Context: <NSManagedObjectContext: 0x7f81b04c75a0>
2015-03-05 00:39:40.434 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setDefaultContext:](0x104396400) Set Default Context: (null)
2015-03-05 00:39:40.434 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setRootSavingContext:](0x104396400) Set Root Saving Context: (null)
2015-03-05 00:39:40.435 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setDefaultContext:](0x104396400) Set Default Context: (null)
2015-03-05 00:39:40.435 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setRootSavingContext:](0x104396400) Set Root Saving Context: (null)
2015-03-05 00:39:40.443 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_contextWithStoreCoordinator:](0x104396400) -> Created Context UNNAMED
2015-03-05 00:39:40.443 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setRootSavingContext:](0x104396400) Set Root Saving Context: <NSManagedObjectContext: 0x7f81b280e5a0>
2015-03-05 00:39:40.444 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_newMainQueueContext](0x104396400) Created Main Queue Context: <NSManagedObjectContext: 0x7f81b04d76c0>
2015-03-05 00:39:40.444 Reports[7123:967179] +[NSManagedObjectContext(MagicalRecord) MR_setDefaultContext:](0x104396400) Set Default Context: <NSManagedObjectContext: 0x7f81b04d76c0>
2015-03-05 00:39:40.446 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c75a0) → Saving <NSManagedObjectContext (0x7f81b04c75a0): *** DEFAULT ***> on *** MAIN THREAD ***
2015-03-05 00:39:40.446 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c75a0) → Save Parents? 1
2015-03-05 00:39:40.447 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c75a0) → Save Synchronously? 1
2015-03-05 00:39:40.448 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c6b00) → Saving <NSManagedObjectContext (0x7f81b04c6b00): *** BACKGROUND SAVING (ROOT) ***> on *** MAIN THREAD ***
2015-03-05 00:39:40.448 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c6b00) → Save Parents? 1
2015-03-05 00:39:40.448 Reports[7123:967179] -[NSManagedObjectContext(MagicalSaves) MR_saveWithOptions:completion:](0x7f81b04c6b00) → Save Synchronously? 1

之后，它就冻结了。不会抛出任何错误，但保存操作也不会完成。

我用NSManagedObjectContext.MR_defaultContext()替换了我使用属性上下文的地方并运行了应用程序并成功保存了数据。

为什么我不能通过初始化程序传递MR_defaultContext()的实例？

Answer 1

您的回溯说明了这一切，您正在建立与持久性商店的太多连接。 MagicalRecord documentation详细说明您应该在App Delegate的didFinishLaunching阶段设置堆栈，或者在您的情况下，在实例化DatabaseManager类时设置堆栈。

因此对MagicalRecord.setupCoreDataStackWithStoreNamed("Records")的调用应移至初始化程序（可能更安全地将其置于dispatch_once块中以防止它被多次设置）

init(context: NSManagedObjectContext) {
    struct Static {
        static var onceToken : dispatch_once_t = 0
    }
    dispatch_once(&(Static.onceToken)) {
        MagicalRecord.setupCoreDataStackWithStoreNamed("Records")
    }
    self.context = context
}

顺便说一句，您只需要在应用程序关闭时调用清理，因此可能在您的App Delegate的willTerminate

中

MagicalRecord一切顺利：）

传递NSManagedObjectContext的实例

1 个答案: