iOS how to store data even if the app is closed - ios

Question

I am doing an iOS app. The goal is to send suggestions from user to improve the service I propose.
The app is a native app. I want to create a global NSMutableArray where I store all the suggestions. The problem is my device can be not connected to internet.
There is two cases:
If the device is connected when the user send his suggestion, it is send.
If not, the suggestion is saved in my NSMutableArray and send later.
Is it possible to create a global variable which store all my suggestions ? If my app is crashed/closed this variable can't be dealloc/reset.
Is a singleton enough to do this ?

Answer 1

first check for internet status of your device.if status is connected then send the array.if status in not connected then save the array into NSUserDefaults.To save suggestions array
NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray * suggestions = [[NSMutableArray alloc] init];
[defaults setObject: suggestions forKey:#"suggestions"];
to Access those suggestions
NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray * suggestions = [[NSMutableArray alloc]initWithArray:[defaultsobjectForKey:#"suggestions"]];

Answer 2

A singleton is not enough because you are going to lose all your data if your app is killed or crashes.
If there are only a few suggestions and they are short, the easiest approach would be to save them in your UserDefaults.
If you are going to save too much suggestions with long texts and several fields you will need to implement a database. Core Data would be a good solution for your problem.

Answer 3

An easy (single line of code) way to do this is to use plists and the command
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)flag
on an NSArray
From the description:
Writes the contents of the array to a file at a given path.
If the array’s contents are all property list objects (NSString, NSData, NSArray, or NSDictionary objects), the file written by this method can be used to initialize a new array with the class method arrayWithContentsOfFile: or the instance method initWithContentsOfFile:. This method recursively validates that all the contained objects are property list objects before writing out the file, and returns NO if all the objects are not property list objects, since the resultant file would not be a valid property list.
In your example you would have (say) an NSArray of NSDictionaries with each NSDictionary containing the suggestions. Calling writeToFile would write it out in the event of no network availability. Then (say on app foreground event) you would read the file (arrayWithContentsOfFile call). If there is any content you would try to push to the server again.

Answer 4

You can use NSUserDefaults.
//write to NSUserDefaults
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:[NSNumber numberWithInteger:userRatingInteger] forKey:#"userRating"];
[defaults synchronize];
//read from NSUserDefaults
NSNumber *userRatingNumber = [defaults objectForKey:#"userRating"];
if (userRatingNumber) { // the user has rated.
// Use the value as needed.
}