Few things to take into account
Then I'd make a function called
User.update() that just pulls userdata
from the server and populates the User class properties. This is the
only function that would be allowed to write over the User properties.
Whoever is familiar with Active Record design pattern would be fooled by the name of the method.
The name could make us belive that we are pushing changes to the server, but in reality -according to the question- we would be doing the opposite!!!
If we are pulling the latest
User representation, then we should consider changing the name of the method for something like retrieve , refresh or reload. If we are really synchronizing, sync would be more acurate than update.
Too many requests
I would run the
User.update() function during times such as:
- App launch
- App re-opened from sleep
- Profile update
- After in-app-purchase
If we need to retrive the
User so often, it probably means that we shouldn't hold all its state. Or at least not completely.1
Ideally, we request the latest data when there's an evidence of changes and we need to be aware of them. For example, after specific business operations.
Otherwise, we come to realise that any event|action|moment is as good as any other. Such randomness, eventually, lead us to retrieve half DB without consistent reasons.
App re-opened from sleep is a good moment for refreshing the
User, why shouldn't it be good for any other entity?
Remember that connections consume resources and they also have an impact on the data plan. So, I would consider constraining the requests to the essential.
Caching only the essential
Consider holding the URIs instead of the complete representantion. For example, we could request and hold data that is unlikely to change.
GET /user/1 HTTP/1.1
HTTP 200 OK
Caching the fullname and hold the URIs of those resources sensibles to changes. For example,
Later, we can retrieve these resources only when the business need them instead of randomly after certain events of the application.
Finally, think who else is going to be changing the
User beside the user himself. If there's no concurrency over the data, probably the client application always has the most up-to-date representation.
1: What we do with the local storage is caching. If we have to expire the cache often, it means either we don't need cache at all or we are caching the wrong data.