What is the difference between:
[[NSUserDefaults standardUserDefaults] registerDefaults:
[NSDictionary dictionaryWithObjectAndKey:anObject, #"something"]];
And this:
[[NSUserDefaults standardUserDefaults] setObject:anObject forKey:#"something"];
The difference is that the first code-snippet you register defaults that will be used when the user has not made any changes to the "property".
So if you want to provide let's say a "property" with the key name 'Welcome message', you could instead of having the property returning nil insert a default message 'Welcome first-time user' that will be displayed when there have been no changes to the property.
This will simplify your logic because you don't need to write an if test to check if the "property" returns nil and then make another message if this is the case.
NSString *greeting = [[NSUserDefaults standardUserDefaults] stringForKey:#"Greeting"];
if(greeting == nil) {
NSLog(#"Welcome first-time user!");
}
The second code-snippet you posted is for setting the property to another value. You will have different set methods (setString, setObject, setBoolean) to set values depending on your program state in the Userdefaults.
EDIT-----Updates as requested in comment.
The first method is for registering values to defaults, as the name implies. The first time you access the property with some key name the value will be either nil for objects, false for booleans or 0 for numbers. Instead of doing a lot of tests and so on to so if the values is not set in the program, and then do something "default" action such as the example above, you can ship your application with some already predefined values for these keys.
A typical place to put the registerDefaults is in the initializer-method in the appDelegate.
Then somewhere in your program you may want to set the values of these fields then you use the setObject, setString, setBoolean...and for retrieving you use stringForKey, objectForKey...
Think of it as this
The registerDefaults is the constructor where you may supply sensible values for the object, otherwise you get some defaults which I already wrote. Then later if you want to change the object's attributes you do NOT use the "constructor" but the set/get methods.
Long story short,
[[NSUserDefaults standardUserDefaults] setObject:#"Entropy" forKey:#"kName"]
will save "Entropy" to a file named com.example.Demo.plist in Library/Preference folder (where com.example.Demo is your Bundle ID, see IOS Application Security Part 20 – Local Data Storage)
[[NSUserDefaults standardUserDefaults] setObject:#"Mac OS X" forKey:#"kOS"];
NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys:
#"Windows", #"kOS",
#"Google", #"kSearchEngine", nil];
[[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];
NSLog(#"%#", [[NSUserDefaults standardUserDefaults] objectForKey:#"kOS"]);
NSLog(#"%#", [[NSUserDefaults standardUserDefaults] objectForKey:#"kSearchEngine"]);
NSLog(#"%#", [[NSUserDefaults standardUserDefaults] objectForKey:#"kBrowser"]);
will print "Mac OS X", "Google", (null)
In fact, registerDefaults
does not save to disk
only sets value for keys that haven't been set ("kOS" is set by setObject:forKey: and "kSearchEngine" is not set)
returns 0 for scalar values, nil for objects if that key is not set by both registerDefaults and setObject:forKey: ("kBrowser" in this case)
And the usage of registerDefaults
Quoted from Preferences and Settings Programming Guide
If these standard default values are not appropriate for your app, you
can register your own default values using the registerDefaults:
method. This method places your custom default values in the
NSRegistrationDomain domain, which causes them to be returned when a
preference is not explicitly set.
Quoted from How to Save Data with NSUserDefaults
Another tip is that you can initialize your NSUserDefaults with a
pre-defined NSDictionary object. So for example you could set a
default value to be “false” or “true” before the user ever had a
chance to interact with your program. In my case, sometimes I create
an array that represents all the levels in my game, and in each array
value I store a boolean to check if a player has finished the level.
To do this I create the data object and then register it with
NSUserDefaults. If a previous value exists for the object, then
nothing happens. Otherwise my blank object gets saved as the “default”
defaults
PS: Ole has a very good article explaining Handling Default Values With NSUserDefaults in detail
Another way of looking at it is this. If you delete the preferences file from ~/Library/Preferences, the defaults that are set by registerDefaults will be the ones that apply to the application until new preferences are set.
In Swift 2.1.1 Xcode 7.2
I added this snippet to application:didFinishLaunchingWithOptions to initialise the tintColorsIndex which is one of parameters user can change in the app.
let defaults = NSUserDefaults.standardUserDefaults()
defaults.registerDefaults([
"tintColorsIndex" : -1,
])
When the app is launched the very first time the tintColorsIndex will be assigned a value of -1 (an Int). If user has changed the color while using the app, their preference won't be overridden at subsequent launches.
User Defaults are grouped in domains...
registerDefaults is used to add defaults to the registration domain..
You can read about the domains in Preferences and Settings Programming Guide.
Related
I have in my code NSUserDefaults but then, when I needed to adjust it, I do something like this:
// OLD save
NSInteger myInt = [prefs integerForKey:#"MYINTEGER"];
// if need to be adjusted will be NEW save
if(myInt > index){
myInt--;
[[NSUserDefaults standardUserDefaults] setInteger:myInt forKey:#"MYINTEGER"];
}
Because my problem is when Im reloading it again, it appears adjusted of course after the NEW save.
Just wondering if, is there a way to just reload the previous save?
Thanks
There is no way to get the previous save using NSUserDefaults if you are using single integer value it will overwrite the last value.instead of single integer value you can take NSArray in NSUserDefaults where last element will give the latest value and previous element give subsequent values. OR try using two keys if you need the previous and new value only.
When you are using the same key,your previous value will be replaced.So you couldn't get the previous value.So use the different key.
I'm trying to call up a specific setting that is saved in the settings bundle of my iphone app. I want to do an if statement based on what was saved. My code in the implementation file looks like this:
branchMatch = [[NSString alloc] initWithString:[defaults objectForKey:#"branch"]];
The object in the settings file is just the name of the specific branch. I keep getting the SIGABRT error but I'm not sure why.
First, there's no need to initialize a string with another string. Assuming that branchMatch is a NSString*, the following would suffice:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
branchMatch = (NSString*)[defaults objectForKey:#"branch"];
Second, check if objectForKey returns a nil. Your SIGABRT is, most likely, due to a nil there.
EDIT: those values aren't present in the collection until the user opens up Settings and explicitly changes them. It's up to you to provide the sensible value if the setting is not found (is nil). The ones in the settings bundle are not automatically applied; they are only for the Settings app to initialize its UI properly.
Are you checking that the objectForKey call isn't returning nil?
Do this instead :
NSUserDefault* defaults = [NSUserDefauls standardUserDefaults];
NSString* setting = [defaults objectForKey:#"branch"];
if (setting)
// Do what needed if branch is set
else
// Do what needed if branch has never been set
After much hair pulling, I realized that I need to load user defaults from the delegate class instead of the ViewController.
Thanks for all the input
I'm aware of NSUserDefaults for saving/restoring user preferences. What is the equivalent class for an application? For example, the application may have a "last run" field; or it may have a field for a unique identification of the device for use at the application level.
My intention is to keep the application's settings (not user's settings) out of the Settings Application, and not backup those settings in iTunes, Time Machine, {whatever}.
I'm getting a lot of noise for Java and C#, but not much for iOS/iPhone/iPad.
NSUserDefaults can be used for what you're asking.
if (![[NSUserDefaults standardUserDefaults] boolForKey:#"shownPrompt"]) {
[[NSUserDefaults standardUserDefaults] setBool:YES forKey:#"shownPrompt"];
// Show your prompt or whatever
}
That's a working code snippet. If the key is false, it sets it to true and shows the prompt. The next time this code runs, the key will already by true, so the prompt won't be shown.
NSUserDefaults is specific to the current app on the current device, and is similar to an NSMutableDictionary in that it's a key-value system, with the difference that instead of instantiating your own, there's a universal shared instance for your whole app, that doesn't get erased when the app exits.
NSUserDefaults is perfect for saving things like whether something has been shown, the date of last run, etc. Read the docs here: https://developer.apple.com/documentation/foundation/userdefaults
Don't be put off by the 'user preferences' part. You can use it to save anything you want (as long as it is or can be converted to an NSObject which implements <NSCoding>, which basically means NSString, NSDictionary, NSArray, NSNumber, UITextField, int, float, bool, etc.).
Just to clarify, stuff you put in NSUserDefaults will not, under any circumstances, automagically turn up in the Settings app. It will be kept completely private and hidden. For something to appear in Settings, you need to add a Settings bundle to your app, and manually add keys to it for each and every value that you want to be visible in the Settings app.
if you can store value by NSUserDefaults, then it is good to store application preferences too.
or add settings.plist on your project and read that (what you are not changing later)
and you can use like.,
+ (NSDictionary*)getBundlePlist:(NSString *)plistName
{
NSString *errorDesc = nil;
NSPropertyListFormat format;
NSString *plistPath = [[NSBundle mainBundle] pathForResource:plistName ofType:#"plist"];
NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
NSDictionary *temp = (NSDictionary *)[NSPropertyListSerialization
propertyListFromData:plistXML
mutabilityOption:NSPropertyListMutableContainersAndLeaves
format:&format errorDescription:&errorDesc];
return temp;
}
+ (id) getPropValue:(NSString *)PropertyName
{ // I am supposing you had add your app preferences on settings.plist.
return [[Property getBundlePlist:#"settings"] objectForKey:PropertyName];
//here Property is my class name, then you can use value by
//NSString *value = [Property getPropValue:#"setting1"];
}
It's hard to tell what you're asking. It sounds like NSUserDefaults is what your looking for, but you claim that you're already aware of it. So what's your problem?
After uninstalling an application completely from the device and then loading it in the debugger, I am attempting in a setup method to load a flag using boolForKey. The first time the app runs I have the expectation that the bool will not exist, since I have just reinstalled the app. I expect from the documentation that boolForKey will therefore return NO.
I am seeing the opposite though. boolForKey is returning YES, which fubars my initial user settings. Any idea why this might be happening or a good way around it?
BOOL stopAutoLogin = [[NSUserDefaults standardUserDefaults] boolForKey:#"StopAutoLogin"];
_userWantsAutoLogin = !stopAutoLogin;
So stopAutoLogin comes out as "YES", which is completely unexpected.
Stranger and stranger: When I call objectForKey:#"StopAutoLogin" I get a nil object, as expected. It's just the boolForKey that returns a bad value. So I changed the code to this:
// this is nil
NSObject *wrapper = [[NSUserDefaults standardUserDefaults] objectForKey:#"StopAutoLogin"];
// this is YES
BOOL stopAutoLogin = [[NSUserDefaults standardUserDefaults] boolForKey:#"StopAutoLogin"];
please try [UserDefaults synchronize];
Because this method is automatically invoked at periodic intervals, use this method only if you cannot wait for the automatic synchronization (for example, if your application is about to exit) or if you want to update the user defaults to what is on disk even though you have not made any changes.
please see: http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html
Do you register the default values for your keys?
NSMutableDictionary *appDefaults = [NSMutableDictionary dictionaryWithCapacity:1];
[appDefaults setObject:#"NO" forKey:kReloadOnStartKey];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults registerDefaults:appDefaults];
If there is no registration domain,
one is created using the specified
dictionary, and NSRegistrationDomain
is added to the end of the search
list.
The contents of the registration
domain are not written to disk; you
need to call this method each time
your application starts. You can place
a plist file in the application's
Resources directory and call
registerDefaults: with the contents
that you read in from that file.
See this link for more information.
Okay, I'm trying to write a high score function for my app.
My problem is that when no high score has been saved yet, my program crashes.
If I save it with:
[[NSUserDefaults standardUserDefaults] setObject:#"[given string]" forKey:#"firstName"];
first, it works fine. However, if I start up the program for the first time and try to view the high scores with the following code:
first = [[NSString alloc] initWithString:[[NSUserDefaults standardUserDefaults] objectForKey:#"firstName"]];
bad things happen.
Basically, is there away to see if nothing yet exist under firstName? Is there a way to initialize without erasing any name that might already be present?
Thanks.
The NSString documentation for initWithString: says
Parameters
aString
The string from which to copy characters. This value must not be nil.
The documentation for objectForKey: says
Return Value
The object associated with the
specified key, or nil if the key was
not found.
The problem seems to be that there is a nil returned when you try to retrieve firstName that doesn't exist yet and try to create a NSString with it as input.
The NSUserDefaults instance method registerDefaults: is meant for exactly this purpose: You can set default values for your preferences that will be overridden by any other value set for the same preference key. Just make sure to call it early enough that it will run before any code that needs to access your preferences.
You could load "first" like this:
first = [[[NSUserDefaults standardUserDefaults] objectForKey:#"firstName"] retain];
if (!first) {
// set default or do something else if there wasn't a value saved
first = #"N/A";
}