KVO对象属性在一对多关系内 [英] KVO object properties within to-many relationship

问题描述

我有一个Core Data to-many关系，包含Parent< --- >> Child。我想设置一个键值观察机制，当任何子对象的属性（例如firstName，lastName）改变它触发一个通知。当使用标准的KVO语法：

I have a Core Data to-many relationship consisting of Parent <--->> Child. I would like to setup a key-value observing mechanism such that when a property (e.g. firstName, lastName) on any of the Child objects changes it triggers a notification. When using the standard KVO syntax:

[self.parentObject addObserver:self forKeyPath:@"children" options:NSKeyValueObservingOptionNew context:NULL]

这只会在关系本身被修改时通知（即，子对象被添加或从关系），而不是当这些Child对象之一的属性改变时。显然，这是它的设计操作，所以没有什么不对的发生，但我怎么能改用KVO来实现我的要求？

this only notifies when the relationship itself is modified (i.e. a Child object is added or removed from the relationship), rather than when a property of one of those Child objects changes. Obviously this is how it was designed to operate, so there's nothing wrong with that happening, but how can I instead use KVO to achieve my desired requirement?

提前感谢！

推荐答案

AFAIK没有内置的方法来观察集合对象属性与一行代码。相反，当对象从集合中插入/删除时，必须添加/删除观察器。

AFAIK there is no built-in way to observe collection object properties with a single line of code. Instead you have to add/remove observers when the object is inserted/removed from your collection.

您可以在这里找到解释和示例项目： https://web.archive.org/web/20120319115245/http://homepage.mac.com/mmalc/CocoaExamples/controllers。 html
（请参阅观察集合与观察集合中对象的属性不同）

An explanation and a sample project can be found over here: https://web.archive.org/web/20120319115245/http://homepage.mac.com/mmalc/CocoaExamples/controllers.html (See the "Observing a collection is not the same as observing the properties of the objects in a collection" section)

更新：

链接已中断 - 我将其更改为archive.org快照。

Update:
The Link broke - I changed it to an archive.org snapshot.

这篇关于KVO对象属性在一对多关系内的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！