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Mastering Swift 4 - Fourth Edition by Jon Hoffman

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How ARC works

Whenever we create a new instance of a class, ARC allocates the memory needed to store that class. This ensures that there is enough memory to store the information associated with that instance of the class, and also locks the memory so that nothing overwrites it. When the instance of the class is no longer needed, ARC will release the memory allocated for the class so that it can be used for other purposes. This ensures that we are not tying up memory that is no longer needed.

If ARC were to release the memory for an instance of a class that is still needed, it would not be possible to retrieve the class information from memory. If we did try to access the instance of the class after the memory was released, there is a possibility ...

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