使用Swift的核心数据瞬态值

问题描述

有没有人知道或有一个例子，如何使用Swift处理核心数据瞬态值？我知道在属性之前使用@NSManaged，但是不能弄清楚如何使用Swift来构建瞬态值的逻辑。

Does anyone know, or have an example of, how to handle core data transient values with Swift? I know to use @NSManaged before the properties, but can't figure out how to code the logic to build the transient values using Swift.

推荐答案

在特定属性（例如 sectionTitle ）的数据模型中选中瞬态字段。

创建类对于该实体，它将类似于

Check mark the transient field in your data model for particular attribute(e.g. sectionTitle).
Create class for that entity, it will look something like

 class Message: NSManagedObject {

    @NSManaged var body: String?
    @NSManaged var time: NSDate?
    @NSManaged var sectionTitle: String?
}

编辑它，如下所示：

class Message: NSManagedObject {

    @NSManaged var body: String?
    @NSManaged var time: NSDate?

    var sectionTitle: String? {
        return time!.getTimeStrWithDayPrecision()
        //'getTimeStrWithDayPrecision' will convert timestamp to day
        //just for e.g.
        //you can do anything here as computational properties
    }
}

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