Best way to check if an iPhone app is running for the first time

I want to check if my iPhone app is running for the first time. I can create a file in the documents folder and check that file to see if this i开发者_Python百科s the first time the app is running, but I wanted to know if there is a better way to do this.

I like to use NSUserDefaults to store an indication of the the first run.

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];  
if (![defaults objectForKey:@"firstRun"])
  [defaults setObject:[NSDate date] forKey:@"firstRun"];

[[NSUserDefaults standardUserDefaults] synchronize];

You can then test for it later...

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];        
if([defaults objectForKey:@"firstRun"])           
{
  // do something or not...
}

Ok what confuses the hell out of me about User Defaults.

WHERE are they stored?

• you dont care it varies per iOS/Mac.
• you just getVALUE by KEY
• setVALUE by KEY + synchronize
• iOS/Mac does the rest.

This is the common use case: Checking for the existence of a value e.g firstRun. The first time it will NOT EXIST so usually followed by setting the value. 2nd Run - on next loop it does exist and other use case/else stmt is triggered

---- .h

@interface MyAppDelegate : UIResponder <UIApplicationDelegate>

//flag to denote if this is first time the app is run
@property(nonatomic) BOOL firstRun;

------ .m

@implementation MyAppDelegate

@synthesize firstRun = _firstRun;

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{

    //============== 
    //Check to see if this is first time app is run by checking flag we set in the defaults

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];  

    if (![defaults objectForKey:@"firstRun"]){
        //flag doesnt exist then this IS the first run
        self.firstRun = TRUE;
        //store the flag so it exists the next time the app starts
        [defaults setObject:[NSDate date] forKey:@"firstRun"];
    }else{
        //flag does exist so this ISNT the first run
        self.firstRun = FALSE; 
    }        
    //call synchronize to save default - where its saved is managed by iOS - varies by device and iOS/Mac
    [[NSUserDefaults standardUserDefaults] synchronize];
    //TO TEST: delete the app on the device/simulator
    //run it - should be the first run
    //close it - make sure you kill it and its not just in the background else didFinishLaunchingWithOptions wont be called
    //just applicationDidBecomeActive
    //2nd run it should  self.firstRun = FALSE;
    //=============

//NOTE IMPORTANT IF YOURE ROOTVIEWCONTROLLER checks appDelegate.firstRun then make sure you do the check above BEFORE setting self.window.rootViewController here

self.window.rootViewController = self.navController;


    [self.window makeKeyAndVisible];
    return YES;
}

---- USING THE FLAG

MyAppDelegate *appDelegate = (MyAppDelegate *)[[UIApplication sharedApplication] delegate];

if (appDelegate.firstRun){
    NSLog(@"IS FIRST RUN - Do something: e.g. set up password");

}else {
     NSLog(@"FPMyMusicScreenViewController: IS NOT FIRST RUN - Prompt for password");
}

The examples above confused me a bit as they show how to check for it the first time but then mention how to 'check for it later' in the same comment. The problem is when we find it doesnt exist we immediately create it and synchronize. So checking for it late actually mean when you RESTART THE APP not in same run as first run.

In your app delegate register a default value:

NSDictionary *defaultsDict = 
[[NSDictionary alloc] initWithObjectsAndKeys:[NSNumber numberWithBool:YES], @"FirstLaunch", nil];
[[NSUserDefaults standardUserDefaults] registerDefaults:defaultsDict];
[defaultsDict release];

Then where you want to check it:

NSUserDefaults *sharedDefaults = [NSUserDefaults standardUserDefaults];
if ([sharedDefaults boolForKey:@"FirstLaunch"]) {
  //Do the stuff you want to do on first launch
  [sharedDefaults setBool:NO forKey:@"FirstLaunch"];
  [sharedDefaults synchronize];
}

You can implement it with the static method below. I think it's better since you can call this method as many times as you like, unlike the other solutions. enjoy: (Keep in mind that it's not thread-safe)

+ (BOOL)isFirstTime{
    static BOOL flag=NO;
    static BOOL result;
    if(!flag){
        if ([[NSUserDefaults standardUserDefaults] boolForKey:@"hasLaunchedOnce"])
        {
            result=NO;
        } else
        {
            [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"hasLaunchedOnce"];
            [[NSUserDefaults standardUserDefaults] synchronize];
            result=YES;
        }

    flag=YES;
    }
    return result;
}

You can use a custom category method isFirstLaunch with UIViewController+FirstLaunch.

- (BOOL)isFirstLaunch
{
    if ([[NSUserDefaults standardUserDefaults] boolForKey:@"kFirstLaunch"]) {
        return YES;
    }
    else {
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"kFirstLaunch"];
        [[NSUserDefaults standardUserDefaults] synchronize];
        return NO;
    }
}

And when you need to use it in controller

BOOL launched = [self isFirstLaunch];

if (launched) {
//if launched
}
else {
//if not launched
}

Use NSUserDefaults. If the sharedDefault has a key for your app, its run before. Of course, you'll have to have the app create at least one default entry the first time the app runs.

Swift:

var isFirstLaunch: Bool {
    get {
        if (NSUserDefaults.standardUserDefaults().objectForKey("firstLaunchDate") == nil) {
            NSUserDefaults.standardUserDefaults().setObject(NSDate(), forKey: "firstLaunchDate")
            NSUserDefaults.standardUserDefaults().synchronize()
            return true
        }
        return false
    }
}

Another tip:

When using NSUserDefaults, these settings will be wiped if the app is ever deleted. If for some reason you require these settings to still hang around, you can store them in the Keychain.