Cocoa (Touch) 到底如何理解

有问题搞不清，就找问题的根，它的根，以下内容来自apple开发网【https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/KeyValueCoding/Articles/KeyValueCoding.html#//apple_ref/doc/uid/10000107i】

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Cocoa and Cocoa Touch are the application development environments for OS X and iOS, respectively. Both Cocoa and Cocoa Touch include the Objective-C runtime and two core frameworks:

Cocoa, which includes the Foundation and AppKit frameworks, is used for developing applications that run on OS X.

Cocoa Touch, which includes Foundation and UIKit frameworks, is used for developing applications that run on iOS.

Note: The term “Cocoa” has been used to refer generically to any class or object that is based on the Objective-C runtime and inherits from the root class,

NSObject

.
The terms “Cocoa” or “Cocoa Touch” are also used when referring to application development using any programmatic interface of the respective platforms.