Save game level in my app even when the app is closed? - ios

Question

I am making an RPG game for the iPhone and everything is working out great but I need to know how to save my game level so that even if the user were to close the app running in the background the entire game wouldn't start over again. I was even thinking of bringing back old style gaming and making it so that you have to enter a password to start from where you left off. But even then I wouldn't know how to save the game properly. Plus even if I did save the game how would I be able to make it stay saved even when the app closes completely? So far I have tried adding save data code to the AppWillTerminate line but still nothing. Any help is appreciated.

Answer 1

I'm not sure if you want to save which level the user was on, or if you want to save the game state. If you simply want to save which level the user was on, you should go with #EricS's method (NSUserDefaults). It's a little more complicated to save game state. I would do something like this:
//Writing game state to file
//Some sample data
int lives = player.kLives;
int enemiesKilled = player.kEnemiesKilled;
int ammo = player.currentAmmo;
//Storing the sample data in an array
NSArray *gameState = [[NSArray alloc] initWithObjects: [NSNumber numberWithInt:lives], [NSNumber numberWithInt:enemiesKilled], [NSNumber numberWithInt:ammo], nil];
//Writing the array to a .plist file located at "path"
if([gameState writeToFile:path atomically:YES]) {
NSLog(#"Success!");
}
//Reading from file
//Reads the array stored in a .plist located at "path"
NSArray *lastGameState = [NSArray arrayWithContentsOfFile:path];
The .plist would look like this:
Using an array would mean that upon reloading the game state, you would have to know the order that you stored the items in, which isn't that bad, but if you want a more reliable method, you could try using an NSDictionary like this:
//Writing game state to file
//Some sample data
int lives = player.kLives;
int enemiesKilled = player.kEnemiesKilled;
int ammo = player.currentAmmo;
int points = player.currentPoints;
//Store the sample data objects in an array
NSArray *gameStateObjects = [NSArray arrayWithObjects:[NSNumber numberWithInt:lives], [NSNumber numberWithInt:enemiesKilled], [NSNumber numberWithInt:points], [NSNumber numberWithInt:ammo], nil];
//Store their keys in a separate array
NSArray *gameStateKeys = [NSArray arrayWithObjects:#"lives", #"enemiesKilled", #"points", #"ammo", nil];
//Storing the objects and keys in a dictionary
NSDictionary *gameStateDict = [NSDictionary dictionaryWithObjects:gameStateObjects forKeys:gameStateKeys];
//Write to file
[gameStateDict writeToFile:path atomically: YES];
//Reading from file
//Reads the array stored in a .plist located at "path"
NSDictionary *lastGameState = [NSDictionary dictionaryWithContentsOfFile:path];
The dictionary .plist would look like this:

Answer 2

To save the level:
[[NSUserDefaults standardUserDefaults] setInteger:5 forKey:#"level"];
To read the level:
NSInteger level = [[NSUserDefaults standardUserDefaults] integerForKey:#"level"];
I would set it whenever the user enters that level. You could wait until you are sent into the background, but there's really no point in waiting.