Being able to measure performance is required针对性能进行度量 in order to determine whether optimizations are needed是否需要优化, and whether the optimizations actually improved ...
Foundation framework提供了两个内置的NSOperation的子类,但是这两个内置的operation不一定能够满足我们的实际的需要。比如我们需要一个完成一个网络请求的operation,里面可能会有许多自定义的逻辑在里面,为了...