Not able to store NSDate into NSUserDefaults
In my application, i want to store the date at which the app is started for the first time.
I'm using following code in application:didFinishLaunchingWithOptions method
NSDate* today = [NSDate date];
[[NSUserDefaults standardUserDefaults] registerDefaults: @{@"CONSCIENCE_START_DATE" : today}];
NSLog(@"%@", [[NSUserDefaults standardUserDefaults] objectForKey:@"CONSCIENCE_START_DATE"]);
But every time when i start the application, its printing the time at which the app is starting. Its not printing the date at which i started the app.
I tried to reset the simulator and ran the code again. Still no success. Can some one point me the error in my code please?
由于您的目标是跟踪用户第一次启动您的应用程序，因此在application:didFinishLaunchingWithOptions需要如下所示application:didFinishLaunchingWithOptions ：
NSDate *date = [[NSUserDefaults standardUserDefaults] objectForKey:@"CONSCIENCE_START_DATE"];
if (!date) {
// This is the 1st run of the app
date = [NSDate date];
[[NSUserDefaults standardUserDefaults] setObject:date forKey:@"CONSCIENCE_START_DATE"]; // Save date
}
NSLog(@"First run was %@", date);
You need to call [[NSUserDefaults standardDefaults] synchronize] after you set the value.
From the Apple Docs:
At runtime, you use an NSUserDefaults object to read the defaults that your application uses from a user's defaults database. NSUserDefaults caches the information to avoid having to open the user's defaults database each time you need a default value. The synchronize method, which is automatically invoked at periodic intervals, keeps the in-memory cache in sync with
a user's defaults database.
You Can store and retrieve in this way
var startDate: NSDate? {
get {
return NSUserDefaults.standardUserDefaults().objectForKey(BCGConstants.UserDefaultsKey.startDateKey) as? NSDate
}
set {
NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: BCGConstants.UserDefaultsKey.startDateKey)
NSUserDefaults.standardUserDefaults().synchronize()
}
}