I am building a very simple app to store data on people like name, age, etc. I give the user the option of changing the data such as when a person has a birthday. I can’t figure out the best way to store the data.
I have searched for a long time now and I can’t find the simple answer that I am looking for. If I change the data in a mutable array will that data be changed permanently? I mean will that write over the existing code and change the data so that it will still exist when the app is closed and reloaded again?
So far I am not able to do that. I have experience in MySql and Sql server so I have a tendency to go that direction if possible, but I would really like to use a mutable array or mutable dictionary if possible. This may be such an elementary question, but I can’t find an answer anywhere.
You have some misconceptions.
The objects you create are in memory. There’s nothing permanent about them. You have to save them somehow or they are gone when you quit the application and come back.
If you want to save an array, you have a number of options.
If the array contains nothing but objects of type NSString, NSData, NSDate, NSNumber, NSArray, or NSDictionary, you can save the array using the system class NSUserDefaults.
NSArray also has a method writeToFile:atomically: that will save an array of data to a file.
If your array contains any objects other than the types I listed above, though, neither of those approaches (NSUserDefaults or writeToFile:atomically) won’t work.
The other option is to use an NSKeyedArchiver to convert the contents of your array to data, and then write that data to a file. In order for that approach to work, every single object i your array, and all the objects in those objects, need to support the NSCoding protocol.
As others have pointed out, you could also use Core Data or mySQL to save your data, but that seems like overkill for just saving an array.