Question

I would like to store a user’s last use of the application and compare it with the current date.

According to the compare I would like to pop a notification on the screen.

How and where do I implement the code of saving the last date? (not in ApplicationWillTerminate as i read in another thread here)
How and where do I implement the code of reading that value?

(It should be a NSDate and use an if statement of course..)

Answer 1

User NSUserDefaults which has been built just for these kinds of things (it’s a persistent key value storage with some limitations). Here is a quick snippet:

NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];

// Write current date & time
[sharedDefaults setObject:[NSDate date] forKey:@"lastUsed"];
[sharedDefaults synchronize]; // This makes sure your changes are written to disk

// Read date & time
NSDate *lastStart = [sharedDefaults objectForKey:@"lastUsed"];

Where you want to place this depends on what exactly you would like to measure.