什么是目标C中的键值编码和键值观察? [英] What is Key-Value-Coding and Key-Value-Observing in Objective C?

问题描述

有人可以简单地解释什么是Key-Value-Coding和Key-Value-Observing吗?请不要提供指向Apple Developer参考文档的链接.我经历了他们.我希望能以非常简单的方式进行解释.

Can someone explain in simple terms what is Key-Value-Coding and Key-Value-Observing? Please don't provide links to Apple Developer's reference Document. I have gone through them. I expect an explanation in very simple terms.

推荐答案

键值编码(KVC)意味着使用字符串访问属性或值.

Key-Value-Coding (KVC) means accessing a property or value using a string.

id someValue = [myObject valueForKeyPath:@"foo.bar.baz"];

可能与以下相同:

id someValue = [[[myObject foo] bar] baz];

键值观察(KVO)使您可以观察对属性或值的更改.

Key-Value-Observing (KVO) allows you to observe changes to a property or value.

要使用KVO观察属性，您需要使用字符串将属性标识为；即使用KVC.因此，可观察对象必须符合KVC.

To observe a property using KVO you would identify to property with a string; i.e., using KVC. Therefore, the observable object must be KVC compliant.

[myObject addObserver:self forKeyPath:@"foo.bar.baz" options:0 context:NULL];

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