When to Cache the data

Q1)开发者_如何转开发 I am designing a iPhone app and want to know on what basis I should take the decision of caching data.

Q2) I have a huge data set which can change frequently. On my app I am showing the data under different categories and is planning to fetch the data from server when a particular category is tapped. This will reduce the data transfer. Also, this data can change frequently but I can store it for let say 30 minutes. What strategy should I take here? Should I store in core data or no caching all together and for each repetitive taps should hit the server?

Please suggest.

What does "hit" mean in this context? Asking the server whether your data is fresh or simply refetching it?

I would suggest that you cache a few MB or so, that you assume that data stays fresh for at least thirty seconds or so (depends on your scenario). If you want the application to feel very fluent, download everything that can be reached with two taps (or so) or less if it isn't yet cached after each tap (as long as that isn't too much data).

You might also want to include a less-data-mode for users who have a traffic-based-costs internet access.

It totally depends upon the frequency of new data. You can cache the data that's to be displayed at the application launch in all your tabs and then let the updated data flow when user makes request for new data.