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swift - 删除时的核心数据 EXC_BAD_ACCESS

问题描述

从 Core Data 中删除对象时获取 EXC_BAD_ACCESS。任何想法如何解决这个问题？可能需要阅读一些核心数据原则（？）

func deleteEntity(_ entity : String) {

        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: entity)

        print("Object count:  \(context.registeredObjects.count)") // prints 0 here
        do {
            let results = try context.fetch(fetchRequest)
            for managedObject in results {
                let managedObjectData : NSManagedObject = managedObject as! NSManagedObject
                if !managedObjectData.isDeleted{
                    context.delete(managedObjectData)  // EXC_BAD_ACCESS here, fetch request returns 1 item here!
                }
            }
            try context.save()
        } catch let error {
            print(error)
        }
    }




Crashed: com.apple.main-thread
0  CoreData                       0x1114c7293 -[NSManagedObjectContext(_NSInternalAdditions) _registerObject:withID:] + 35
1  CoreData                       0x1114c5569 -[NSManagedObjectContext(_NSInternalAdditions) _retainedObjectWithID:optionalHandler:withInlineStorage:] + 217
2  CoreData                       0x1114d0512 _PF_FulfillDeferredFault + 882
3  CoreData                       0x1114dfe9e _PF_Handler_Primitive_GetProperty + 110
4  CoreData                       0x1114dfca3 -[NSManagedObject(_NSInternalMethods) _newPropertiesForRetainedTypes:andCopiedTypes:preserveFaults:] + 323
5  CoreData                       0x1114dfb39 -[NSManagedObject(_NSInternalMethods) _newAllPropertiesWithRelationshipFaultsIntact__] + 89
6  CoreData                       0x1114dfa2b -[NSManagedObjectContext(_NSInternalChangeProcessing) _establishEventSnapshotsForObject:] + 75
7  CoreData                       0x1114f7168 -[NSManagedObjectContext deleteObject:] + 136

编辑：上下文似乎有问题。我也尝试删除整个商店，但似乎保留了一件，导致崩溃。稍后在不同的视图中添加此特定项目。也许这与人际关系有关。-com.apple.CoreData.ConcurrencyDebug 1使用堆栈跟踪进行调试 也显示

“一个 NSManagedObject 可能只在一个 NSManagedObjectContext 中（或被一个 NSManagedObjectContext 观察）。”

标签： swiftcore-datansmanagedobjectcontext

解决方案

删除实体的所有对象的常用方法是

func deleteEntity(_ entity : String) throws {
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: entity)
    let results = try context.fetch(fetchRequest)
    for managedObject in results {
       context.delete(managedObject) 
    }

    try context.save()
}

但是在 iOS 9+、macOS 10.11+ 中有更好的方法

func deleteEntity(_ entity : String) throws {
    let fetchRequest = NSFetchRequest<NSManagedObject>(entityName: entity)
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: request as! NSFetchRequest<NSFetchRequestResult>)
    let persistentStoreCoordinator = context.persistentStoreCoordinator!
    try persistentStoreCoordinator.execute(deleteRequest, with: context)

    try context.save()
}

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