swift - 如何确认核心数据执行

Question

我正在尝试确认核心数据中的所有数据是否已通过以下来源删除(其中“CoreDataHelper.getCoreDataHelper().context”是 NSManagedObjectContext)

public static func delete(predicates: [NSPredicate] = []) {
    let fetchRequest = request(predicates: predicates)
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
    do {
        let result1 = try CoreDataHelper.getCoreDataHelper().context.fetch(fetchRequest)
        NSLog("Delete batch size: %d", result1.count)
        let result2 = try CoreDataHelper.getCoreDataHelper().context.execute(deleteRequest)
        NSLog("Delete request succeeded: %d", result2)
    } catch {
        NSLog("Delete request failed")
        return
    }
}

当我测试它时，日志中显示以下内容

Delete batch size: 1

Delete request succeeded: 250432

但是实际看到数据的时候，好像并没有删除。我尝试添加数据，因为发生错误，数据已经在核心数据中。

public static func add(from object: Dictionary<String, Any>) -> NSManagedObjectProtocol? {
    let exists = fetch(id: object)
    if exists.count > 0 {
        NSLog("Object already exists in CoreData : %@", object.description)
        return nil
    } else {
        return newObject(object: object) as NSManagedObjectProtocol
    }
}

Object already exists in CoreData : ....

所以我的问题是我怎么知道 NSBatchDeleteRequest 的执行功能是否正常工作。是否有一个返回值可以用来确认执行是否没有错误？

Answer 1

删除后保存你的NSManagedContext:

public static func delete(predicates: [NSPredicate] = []) {
    let fetchRequest = request(predicates: predicates)
    let deleteRequest = NSBatchDeleteRequest(fetchRequest: fetchRequest)
    do {
        ...
        let result2 = try CoreDataHelper.getCoreDataHelper().context.execute(deleteRequest)
        //save context
        try CoreDataHelper.getCoreDataHelper().context.save()
    } catch {
        NSLog("Delete request failed")
        return
    }
}