I need to store a boolean value that would persist only for the app's running time. When the user quit the app (from the background as well) that variable should reset to default. How can I do this?
I tried constants. I keep constants in a separate .h file. In it I declared it like this.
const BOOL hasShownTutorial = NO;
And in the view controller,
if (hasShownTutorial == NO) {
[self showAppTutorial];
hasShownTutorial = YES;
}
I get an error at hasShownTutorial = YES; saying Read-only variable is not assignable.
I also tried going about this using NSUserDefaults. But the thing is the value is stored for good once you set it. Is there a way to clear it up when the app quits?
I'd appreciate your input and suggestions.
Thank you.
Store it in NSUserDefaults under a specific key.
[[NSUserDefaults standardDefaults] setBool:<myBool> forKey:#"myKey"];
Then to retrieve it later.
BOOL b = [[NSUserDefaults standardDefaults] boolForKey:#"myKey"];
If you want to clear the data.
NSString *domain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:domain];
For example, in your AppDelegate's implementation of -applicationWillTerminate:, just clear the data.
- (void)applicationWillTerminate:(UIApplication *)application
{
NSString *domain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:domain];
}
Edit: If the first method of clearing the data does not work, you can use the class method +resetStandardUserDefaults. For example the following would clear the current defaults.
[NSUserDefaults resetStandardUserDefaults];
A third possiblity is to specifically remove a property.
[[NSUserDefaults standardUserDefaults] removeObjectForKey:#"myKey"];
You can't change const value since it is a read only memory. Use static keyword instead.
Related
I am doing a project in objective-c and I have to store some values in userDefaults. I am already did the same thing in the same project. It was working fine but now I am trying to add some values in userDefaults it showing error while fetch any data from userDefaults. I am adding the datas as,
NSString * totalBitValue = [NSString stringWithFormat:#"%.6f Bit",
totalValue /
[[[NSUserDefaults standardUserDefaults] objectForKey:#"Bit"] floatValue]];
[[NSUserDefaults standardUserDefaults]setObject:totalBitValue forKey:#"totalBTCValue"];
[[NSUserDefaults standardUserDefaults]setFloat:totalUSDValue forKey:#"totalUsedValue"];
[[NSUserDefaults standardUserDefaults] synchronize];
and the error as ,
error: Trying to put the stack in unreadable memory at: 0x7ffeeafe2af0
I got the error in the following line,
if( [[NSUserDefaults standardUserDefaults] objectForKey:#"CoinValue"] != nil) {
[[self ValueLabel] setText: [NSString stringWithFormat:#"%#", [[NSUserDefaults standardUserDefaults] objectForKey:#"CoinValue"] ]];
}
Anyone can help me.Thanks in advance
The reason for your issue is because your code gets recursion.
As I understand, you used NSNotificationCenter to observer key NSUserDefaultsDidChangeNotification. So whenever NSUserDefaults is updated, it will trigger defaultsChanged method. But inside it, you continue to change NSUserDefaults, set new value for totalBTCValue and totalUSDValue (as I guess) which makes defaultsChanged be called again and leads to recursion.
To fix the issue, you shouldn't update NSUserDefaults inside defaultsChanged method
I need to load user data, but I need to do it looped. (always loading). My code is
NSString *savedValue = [[NSUserDefaults standardUserDefaults]
stringForKey:#"preferenceName"];
And also, whenever I make an if function, for example
if (t1activity == "active")
{
//code here
}
I get an error saying Expected identifier or '('
Thanks so much! (objective-c)
In the case the value differs only between YES/NO is better to provide a BOOL.
BOOL isUserActive = [[NSUserDefaults standardUserDefaults] boolForKey:#"preferenceName];
and the set method:
[[NSUserDefaults standardUserDefaults]
setBool:YES
forKey:#"preferenceName"];
Then the decision is simpler:
if(isUserActive) {
{
//code here
}
I was curious to know, how often the NSUSerDefaults do update. Here the Apple Docs.
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.
Is it possible to save and load data on Today Extension using NSUserDefaults?
After closing the Notification Center, the widget behaves like an app which is terminated, so any data results lost. How could I solve this issue?
This is my code:
NSUserDefaults *defaults;
- (void)viewDidLoad {
[super viewDidLoad];
defaults = [NSUserDefaults standardUserDefaults];
NSArray *loadStrings = [defaults stringArrayForKey:#"savedStrings"];
if ([loadStrings objectAtIndex:0] != nil) {
[display setText:[NSString stringWithFormat:#"%#", [loadStrings objectAtIndex:0]]];
}
if ([loadStrings objectAtIndex:1] != nil) {
calculatorMemory = [NSString stringWithFormat:#"%#", [loadStrings objectAtIndex:1]].doubleValue;
}
}
- (IBAction)saveData:(id)sender {
NSString *displayString;
NSString *memoryString;
NSArray *saveStrings = [[NSArray alloc] initWithObjects: displayString, memoryString, nil];
defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:saveStrings forKey:#"savedStrings"];
[defaults synchronize];
}
You need to use app group identifier instead of com.*
For instance:
NSUserDefaults *shared = [[NSUserDefaults alloc]initWithSuiteName:#"group.company.appgroup"];
Don't forget to synchronise when you store data
[shared synchronize];
You need to add the App Group stuff detailed under here and then if it actually worked (pretty iffy under beta) it should allow you to share NSUserDefault data like normal between the host and widget.
Edit: Normal NSUserDefaults does not work. Apple has implemented a new method. To use, simply redefine your NSUserDefaults instance like this:
NSUserDefaults *shared = [[NSUserDefaults alloc]initWithSuiteName:#"com.you.app.container"];
For anyone wondering how in the world do you save and get values then look at this code.
In your regular app add this to save whatever you like in your *.m file.
NSUserDefaults *shared = [[NSUserDefaults alloc]initWithSuiteName:#"group.yourcompanyname.TodayExtensionSharingDefaults"];
//save dic
[shared setObject:dictionary2 forKey:#"dicForTodayWidget"];
//save array
[shared setObject:tempArray2 forKey:#"arrayForTodayWidget"];
//save some value
[shared setObject:#"1234" forKey:#"myValForTodayWidget"];
[shared synchronize];
In your today widget under TodayViewController.m in viewDidLoad add this.
NSUserDefaults *shared = [[NSUserDefaults alloc]initWithSuiteName:#"group.yourcompanyname.TodayExtensionSharingDefaults"];
//get dic
NSMutableDictionary *dictionary = [shared objectForKey:#"dicForTodayWidget"];
You first need the App Groups set up for both targets (application and the extension).
Then, use the
NSUserDefaults *shared = [[NSUserDefaults alloc]initWithSuiteName:#"group.company.myapp"];
to obtain the defaults object which you can read from/write to as usual.
If you want to be notified of changes to the defaults, use the NSUserDefaultsDidChangeNotification in your widget (or app).
For a step-by-step tutorial explaining all this, take a look at this blog post.
#edukulele
Today Extension and Main app run on two processes. Today Extension can't receive NSUserDefaultsDidChangeNotifications. I tried use MMWormhole. It is very good.
I have created a Prefs Controller class, which dose what it says controlls my prefs values. I have two specific values in my prefs both strings one that's called installSelected and the other called finishSelected, I setting them as a string that's either T or F...
When the app first starts I create the new prefs and the values are set to F automatically as those are their default values in the plist bundle. Then later in the app I overwrite installSelected to T. When I restart the application it returns the correct value as T. Then I write over it again using F. Again I restart but when I read the values this time it still shows T when it should be F.
I have debugged this and I am just not sure why it's not saving the value.
This is what my prefController method looks like that is used to write the new values:
- (void) writeBool:(NSString *)name MyBool:(NSString *)myboolString {
prefs = [NSUserDefaults standardUserDefaults];
if ([name isEqualToString:#"InstallsSelected"]) {
[prefs setObject:myboolString forKey:name];
}
else if ([name isEqualToString:#"FinishSelected"]) {
[prefs setObject:myboolString forKey:name];
}
[prefs synchronize];
}
I call the above method like this
[prefsController writeBool:#"InstallsSelected" MyBool:#"F"];
It just makes no sense that it's not working as I am able to change it from F to T but not back if needed and none of the code is different. What might be causing this problem?
Why are you using strings instead of bool values?
You have to set your boolean by using:
// Notice setBool
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:#"pref"];
and call synchronize after it:
[[NSUserDefaults standardUserDefaults] synchronize];
To retrieve the value, you call:
// Notice boolForKey
if(![[NSUserDefaults standardUserDefaults] boolForKey:#"pref"]) {
// False
} else {
// True
}
To register default prefs, use:
NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], #"pref1",
[NSNumber numberWithBool:YES], #"pref2",
nil];
NSUserDefaults * prefs = [NSUserDefaults standardUserDefaults];
[prefs registerDefaults:appDefaults];
Are you on the simulator or a real device? I have had serious problems getting the sync right in the Simulator. It turns out that if you just do a rebuild from xCode, the user preferences are not saved. They are saved if you bring the app to the background in the Simulator (press cmd-shift-H).
Also it helps to NSLog as much as possible to see what is written in the prefs.
I wrote these lines in my code:
CFUUIDRef identifier = CFUUIDCreate(NULL);
NSString *identifierString = (NSString*)CFUUIDCreateString(NULL, identifier);
NSLog(#"%#",identifierString);
[self setValue:identifierString forKey:kParamNameDeviceId];
But these lines are getting called every time when the app launches.
Now my question is, how can the following be achieved?
Create CFUUID.
Store it in some variable in such a way that, when next time my app starts, it should not create a new CFUUID. It should look for the previously created CFUUID and return it.
In short, I want a CFUUID be created ONCE and used throughout the life of the app (till it gets uninstalled).
easiest way is to store it in NSUserDefaults
NSString *identifierString = [[NSUserDefaults standardUserDefaults] objectForKey:#"myID"];
if (!identifierString) {
CFUUIDRef identifier = CFUUIDCreate(NULL);
identifierString = (NSString*)CFUUIDCreateString(NULL, identifier);
[[NSUserDefaults standardUserDefaults] setObject:identifierString forKey:#"myID"];
}
NSLog(#"%#",identifierString);
/* ... */
Create once. Add it in NSUSerDefaults and check whether you have a UUID stored already before creating one. Simple Pseudo code,
NSString *CFUUID = nil;
if (![[NSUserDefaults standardUserDefaults] objectForKey:#"UUID"]) {
//create CFUUDID.
[[NSUserDefaults standardUserDefaults] setObject:CFUUID forKey:#"UUID"];
}
else
{
CFUUID = [[NSUserDefaults standardUserDefaults] objectForKey:#"UUID"];
}
If you are storing identifier on server to keep track of important information regarding unique user than i suggest you store identifierString in "KeyChain" which keeps that identifier even if you application has been deleted by user.
NSUserDefaults keep data until app is deleted. Keychain keeps data even if app is deleted.
I had similar case so this might help if your case is equivalent to mine.