观察器对象订阅那些报告所监视实体中任何状态更改的事件，然后基于那些事件中的信息更新自己的状态。
The observer object subscribes to events that report any state changes in the monitored entity, and then updates its own state based on information in those events.
虽然我们可以通过启用系统监视器来简单观察内存的使用量，但是它不会告诉我们比整个系统内存状态更有用的任何内容。
While we can simply watch the amount of memory used by a script by turning the system monitor on, it will not tell us anything more useful than the status of the entire system memory.
通过忆阻器的电流可以改变它的电阻状态，但是在实际环境中观察随之而来的材料改变是一个挑战。
Electrical charge flowing through a memristor changes the resistance state of the device, but actually observing the corresponding material changes has been a challenge.
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