swift - 将数据保存在 Swift 的 Core Data 中

Question

我目前正在将 Objective C 应用程序更新到 Swift 3。如何保存与从上一个表传递的对象关联的输入数据？ Objective C 应用程序运行良好，但我无法弄清楚 Swift 3 的等效语法是什么。

objective-c 代码是:

- (void)insertNewObject:(NSString*) strRain;
{
NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext];
NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity];
Rainfall *altRainfall = (Rainfall*)[NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context];

altRainfall.gauge = strRain;
altRainfall.primaryGauge = self.detailItem;
altRainfall.dateRecorded = todaysDate;
altRainfall.sortDate = [NSDate date];

NSError *error = nil;
if (![context save:&error])
{
    NSDictionary *dict = [error userInfo];
    NSString *errMsg = [dict valueForKey:@"errMessage"];

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Note" message:errMsg delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil];

    [alert show];

    [self.managedObjectContext deleteObject:altRainfall];
}}

Swift 3 代码是:

    func save(strRain: String) {

    let entity = NSEntityDescription.entity(forEntityName: "Rainfall", in: coreDataStack.context)!
    let newRainfall = NSManagedObject(entity: entity, insertInto: coreDataStack.context)
    newRainfall.setValue(strRain, forKeyPath: "gauge")
    newRainfall.setValue(todaysDate, forKeyPath: "dateRecorded")
    newRainfall.setValue(sortDateItem, forKeyPath: "sortDate")


    print(strRain)
    print(todaysDate)
    print(sortDateItem)

    do {
        try coreDataStack.context.save()
    } catch let error as NSError {
        print("Could not save. \(error), \(error.userInfo)")
    }
}

那么，如何用 Swift 中的内容替换 altRainfall.primaryGauge = self.detailItem 呢？

Answer 1

用于保存和更新数据。

 func saveToDataBase(data:[TestData]){
        for data1 in data{

            let request:NSFetchRequest<TestData> = TestData.fetchRequest()
            do {
                let count = try managedObjectcontext.count(for: request)
                if count == 0 {
                    // save data according to your requirement.
                    print(data1)
                }else{

                    //if anything you want to update then wright here
                }

            }catch{
                let error  = error as NSError
                print("\(error)")
            }
        }
    }

您可以这样做来检索数据。

func retriveSaveData(){

    let request:NSFetchRequest<TestData> = TestData.fetchRequest()
    do {
        let data = try managedObjectcontext.fetch(request) as [TestData]

        if let str = data.first?.name{
            // Your retrieve data
            print(str)
        }
    }catch{
        let error  = error as NSError
        print("\(error)")
    }
}

希望对您有帮助。如果你去看 coredata manager 那么我已经制作了示例项目。 project sample