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.
Related
I am creating a names generator app for iPhone and this is what I am trying to do.
Allow the user to save the current generated name by clicking a save button.
In order to do this, here is what is happening:
The current babyname is displayed in a UILabel.
The user presses 'save' and then the label.text value is appended to a NSMutableArray (I don't think this is working in my code correctly).
The NSMutableArray is then saved in NSUserDefaults.
The contents will then be loaded in another view to populate UITableView cells.
My specific question is, am I handling this saving/persistent storage process correctly? Here is the snippet in question:
- (IBAction)saveName:(id)sender {
// save current baby name to array
NSMutableArray *babyNameArray = [[NSMutableArray alloc] init];
[babyNameArray addObject:babyname.text];
// save list of babynames to nsuserdefaults
[[NSUserDefaults standardUserDefaults] setObject:babyNameArray forKey:#"My Key"];
// for testing log names listed in nsuserdefaults
NSLog(#"%#", [[NSUserDefaults standardUserDefaults] dictionaryRepresentation]);
}
Here is a link to the pastebin of the whole file contents (with comments): http://pastebin.com/hQRM9Azh
Every time you add, you're starting again with an empty array ([[NSMutableArray alloc] init]) – instead of starting with the existing items.
Here's some code which adds to the existing entries instead:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *babyNameArray = [[defaults stringArrayForKey:#"My Key"] mutableCopy];
if (!babyNameArray) babyNameArray = [[NSMutableArray alloc] init];
[babyNameArray addObject:babyname.text];
[defaults setObject:babyNameArray forKey:#"My Key"];
[defaults synchronize];
A couple of things before we start addressing the big issue. First, you'll want to have those arrays of names stored somewhere in a file(s), which you'll read either when the application starts, or in ViewWillAppear/ViewWillLoad.
Second, the way you have things working right now, you will only save one name at a time. You alloc & init a new (empty) array every time the user clicks the "Save Name" button. You then add the current name to this (empty) array and set it as the object for key "My Key." Note that your "My Key" object will always have only one element - the most recently saved name.
And lastly, you never actually save your changes to NSUserDefaults. If I recall correctly, after you are done making changes to it, you need to call synchronize - otherwise your changes will be lost as soon as the application closes. Which kind of kills the whole purpose of using data persistance. :)
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
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.
i m making an iphone app that displays data from a website on a table view .basically i m atoring the website's data in an array and then display it on a table. now i want whenever the website update their data the user get the date when the data was updated .can anybody tell some different ways to do it?
So, are you storing (caching) the website's data on the phone and only updating once in a while, or are to loading the website and populating the table every time the app starts?
If you are not storing it (with Core Data, User Defaults, NSKeyedArchiver, etc.) it will be difficult for how can you tell that the data has changed?
In that case (not storing) you could after having pulled the data from the website generate the hash value of the data and store it using NSUserDefaults along with a NSDate.
The next time you pull the information from the website you will generate the hash again and compare it to the previous value. If they match, then the content was not updated, else it was and you store the new hash value and the current date.
If you have control over the website you can do a couple of things.
Return a HTTP header with information about when the website was last updated and compare it with a date stored locally. This will allow you to use the HEAD HTTP semantic to check if a full GET request is needed allowing you to minimize network access.
Implement push notifications (does seem over-kill for your situation) telling the user that the content was updated.
Best of luck.
UPDATE
So your best bet would be calling [myArray hash] and store it in NSUserDefaults, e.g.
NSUInteger hashValue = [myArray hash];
NSDate *now = [NSDate now];
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[prefs setObject:hashValue forKey:#"hash"];
[prefs setObject:now forKey:#"date"]; // Maybe you have to convert the date to a string.
[prefs synchronize];
And later load it when the app starts (or becomes active):
// Load the website again and generate the hash.
NSUInteger newHashValue = [myArray hash];
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
NSUInteger *oldHashValue = [prefs stringForKey:#"hash"];
NSDate *contentDate;
if (newHashValue == oldHashValue)
{
contentDate = [prefs dateForKey:#"date"];
}
else
{
contentDate = [NSDate now];
// Store the new date.
// and the new hash.
}
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";
}