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NSObject is the root class of most class hierarchies in Objective-C. usually, when using NSObject objects, we will use [[NSObject alloc] init] or [NSObject new] to create object instances. Through this article, we will study the object creation process of NSObject together. initialization Call alloc mode When we call the [NSObject alloc] ...

preface *** KVO official document link I Share some details about KVO 1.context function First, let's take a look at the description of context addObserver:forKeyPath:options:context: the context pointer in the message contains any data, which will be returned to the observer in the corresponding change notification. You can specify NULL ...