Question

我在Record中有一个名为core-data的实体。问题是我无法在操作后保存对象，如下所示：

extension Records {
@nonobjc public class func createFetchRequest() -> NSFetchRequest<Records> {
    return NSFetchRequest<Records>(entityName: "Records")
}

@NSManaged public var datetime: Date
@NSManaged public var year: Int64
@NSManaged public var month: Int16

public override func willSave() {
    super.willSave()

    if (self.datetime != nil) {

        self.year = Int64(datetime.year())
        self.month = Int16(datetime.month())
    }
}
}

extension Date {
    func month() -> Int {
        let month = Calendar.current.component(.month, from: self)
        return month
    }

    func year() -> Int {
        let year = Calendar.current.component(.year, from: self)
        return year
    }
}

这是我遇到的错误信息：

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to process pending changes before save.  The context is still dirty after 1000 attempts.  Typically this recursive dirtying is caused by a bad validation method, -willSave, or notification handler.

Answer 1

来自Apple Documentation：

如果要更新持久属性值，则应该通常测试任何新值与现有值的相等性在做出改变之前。 如果使用标准更改属性值访问器方法，Core Data将观察结果的变化通知，因此在保存对象之前再次调用willSave 托管对象上下文。如果继续修改willSave中的值， willSave将继续被调用，直到您的程序崩溃。

因此，对于wilSave方法，请在保存self.year时重新检查＆amp;需要分配self.month。否则，在不进行检查的情况下为其分配值将再次调用willSave。

//your code
public override func willSave() {
    super.willSave()

        guard let dettime = datetime else {
            return
        }

        if self.year != Int64(datetime.year()) {
            self.year = Int64(datetime.year())
        }

        if self.month != Int64(datetime.month()) {
            self.month = Int16(datetime.month())
        }
    }
// your code

在CoreData中保存操纵值会导致错误

1 个答案: