NSUserDefaults, is a good practice to create local value too?

I'd like to know if creating a mirror of values saved in UserDefault is a good practice or not?

For example if I store parameter "A" in UserDefault is it useful to 开发者_开发知识库maintain a copy of this value locally and update it when UserDefault changes?

In my app I had the necessity to frequently read parameter "A", and in this case I think it's better to read from an ivar instead of from a NSUserDefault, but I'm not sure about that so I'm asking if there is a good practice to follow.

Seems like extra work and a premature optimization to me.

In all my apps I've always retrieved the NSUserDefaults each time they were needed and it was never an issue. Keeps the code short and obvious. And if it becomes a problem, you fix it, easy as that.

The performance is irrelevant because NSUserDefaults is not intended to hold much information or be used so often as to cause a performance problem.

As for code encapsulation and reuse, don't use NSUserDefaults directly on code that performs specific tasks unrelated to your preferences. eg: a method to colorize an image should take the user preference as a parameter instead. Use it directly anywhere else.