How is Cocoa : addObserver working under the hood?

Question

how does addObserver: works under the hood ? Since Objective C can't overload operators...

Are class @properties, or object references stored implicitly in a NSDictionary, which can monitor value access ? Or how can cocoa observe values ?

And especially when we write the getter and setter of property by ourself, how does the observer notification happen?

You should have a look at [this article](http://mikeash.com/pyblog/friday-qa-2009-01-23.html). It explains how the KVO mechanism creates subclasses at runtime and overrides the observed setter methods. — Nicolas Bachschmidt, Dec 19 '11 at 10:18

score 6 · Accepted Answer · answered Dec 19 '11 at 12:29

6

The KVO mechanism creates subclasses at runtime and overrides the observed setter methods. This excellent article of Mike Ash explains how it is implemented.

answered Dec 19 '11 at 12:29

Nicolas Bachschmidt

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How is Cocoa : addObserver working under the hood?

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