How do I store a class object to file?

If you're talking about preserving a few variables within your app, I suggest using NSUserDefaults as they're a pretty simple way of storing / retrieving variables.

If you're talking about having large amounts of data which should be shared outside of your app... I don't think I've ever had to do that... do NSDocuments exist on iOS? They might do that kind of thing...

 

I recently ran into this specific situation with my own project. It's quite simple really, using NSKeyedArchiver and the NSCoding protocol. I adapted this tutorial to my project and frankly, it was done and debugged in barely half a day (my project is quite large too, this method is very adaptable and flexible) :

http://www.raywenderlich.com/1914/how-to-save-your-app-data-with-nscoding-and-nsfilemanager

You're basically going to need to implement 2 extra methods in your class, -(id) initWithCoder: (NSCoder *)aDecoder and -(void) encodeWithCoder: (NSCoder *)aCoder

Saving and loading is basically creating a NSMutableData set from your object and using that class' - (BOOL)writeToFile: (NSString *)path atomically: (BOOL)useAuxiliaryFile; once your object is stored in an instance using NSKeyedArchiver (which will call your implementation of encoderWithCoder).

 

Here's an article on archiving eligible objects into a storable data type (NSData) using NSCoding: http://samsoff.es/posts/archiving-objective-c-objects-with-nscoding

 

You want to save the values for all the properties/data items of the class.