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在AFNetworking源代码AFURLSessionManager.m,为什么在addObserver:forKeyPath:options:AFNetworking中使用forKeyPath中的NSStringFromSelector(@selector(countOfBytesReceived))?
(NSURLSessionTask *)task
[task addObserver:self
forKeyPath:NSStringFromSelector(@selector(countOfBytesReceived))
options:NSKeyValueObservingOptionNew
context:NULL];
为什么使用 “NSStringFromSelector(@selector(countOfBytesReceived))”,而不是@ “countOfBytesReceived”。
[哪种方法用于KVC?](https://stackoverflow.com/q/15023832/4244136) – Willeke