Trying to Save/Load Array Data to Plist - iphone

Question

I've been learning Objective C and the iPhone SDK gradually, and my current project involves building an application that stores numerical data (sports data). This is primarily for learning purposes, as there are multiple apps that do the same thing. Anyway, I've hit a bit of a snag. My intention is to have a list of players stored in a table and allow the user to add additional players.
At the moment, I have a button that when pressed, "Ninjas" will be added to the table. I've also enabled deleting in the table. Unfortunately, I can't seem to figure out how to save and load the data from a plist. I followed various tutorials and guides, but I can't figure out what's happening. My suspicion is I am loading the data from an empty array and adding to that array, but the array involving the data is a separate array from the plist. Unfortunately, I am a bit lost beyond that.
The data in my array is erased whenever I switch views. However, I've noticed that the data remains if I leave and come back, but not if I leave for a considerable amount of time, leave and restart the iphone, etc. This seems to occur even for apps that I have not worked on saving. Is this just a function of the iPhone holding onto data in case a user accidentally exits a program?
Hopefully I explained my issue somewhat tangibly. TL:DR version: I want to add data to an array, save it to a plist, and reload the data from the plist whenever the array is present on the screen. Code below is attempting to accomplish this, but it isn't succeeding.
Thanks
#import "RootViewController.h"
#import "NewPlayer.h"
#import "OptionsMenu.h"
#implementation RootViewController
#synthesize createdPlayers;
#synthesize listOfPlayers;
-(NSString *) pathOfFile{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentFolder = [paths objectAtIndex:0];
return [documentFolder stringByAppendingFormat:#"myfile.plist"];
}
-(void)applicationWillTerminate:(NSNotification*)notification{
NSMutableArray *array = [[NSMutableArray alloc]init];
[array writeToFile: [self pathOfFile] atomically:YES];
}
- (void)viewDidLoad
{
NSString *filePath = [self pathOfFile];
if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {
NSArray *array = [[NSArray alloc]initWithContentsOfFile:filePath];
listOfPlayers.array = [array objectAtIndex:0];
[array release];
}
UIApplication *app = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(applicationWillTerminate:) name:UIApplicationWillTerminateNotification object:app];
[super viewDidLoad];
listOfPlayers = [[NSMutableArray alloc] init];
}
-(IBAction)AddButtonAction:(id)sender{
[listOfPlayers addObject:#"Ninjas"];
[createdPlayers reloadData];
}
-(IBAction)switchView:(id)sender{
OptionsMenu *second = [[OptionsMenu alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:second animated:YES];
}
-(IBAction)newView:(id)sender{
NewPlayer *second = [[NewPlayer alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:second animated: YES];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
}
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return [listOfPlayers count];
}
// Customize the appearance of table view cells.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
// Configure the cell.
cell.textLabel.font = [UIFont fontWithName:#"Helvetica" size:15];
cell.textLabel.textColor = [UIColor whiteColor];
cell.textLabel.textAlignment = UITextAlignmentCenter;
NSString *cellValue = [listOfPlayers objectAtIndex:indexPath.row];
cell.textLabel.text = cellValue;
return cell;
}
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
return YES;
}
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
NSLog(#"delete section: %d rol: %d", [indexPath indexAtPosition:0], [indexPath indexAtPosition:1]);
[listOfPlayers removeObjectAtIndex:[indexPath indexAtPosition:1]];
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
}
else if (editingStyle == UITableViewCellEditingStyleInsert)
{
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view.
}
}
-(void)tableView:(UITableView *)listOfPlayers moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath{
}
-(void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];
// Relinquish ownership any cached data, images, etc that aren't in use.
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
// For example: self.myOutlet = nil;
}
- (void)dealloc{
[createdPlayers release];
[listOfPlayers release];
[super dealloc];
}
#end
#import <UIKit/UIKit.h>
#interface RootViewController : UIViewController <UITableViewDelegate, UITableViewDataSource> {
IBOutlet UITableView* createdPlayers;
IBOutlet UIButton* superCat;
NSMutableArray *listOfPlayers;
}
#property(nonatomic, retain) IBOutlet NSObject *listOfPlayers;
-(NSString *) pathOfFile;
-(void)applicationWillTerminate:(NSNotification*)notification;
-(IBAction)AddButtonAction:(id)sender;
-(IBAction)switchView:(id)sender;
-(IBAction)newView:(id)sender;
#property (nonatomic, retain) UITableView* createdPlayers;
#end
Code update 20th Dec:
-(NSString *) pathOfFile{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentFolder = [paths objectAtIndex:0];
return [documentFolder stringByAppendingFormat:#"myfile.plist"];
}
-(void)applicationWillTerminate:(NSNotification*)notification
{
[self.listOfPlayers writeToFile:[self pathOfFile] atomically:YES encoding:NSUTF8StringEncoding error:NULL];
}
- (void)viewDidLoad
{
self.listOfPlayers = [[NSMutableArray alloc] init];
NSString *filePath = [self pathOfFile];
if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {
NSArray *array = [[NSArray alloc]initWithContentsOfFile:filePath];
self.listOfPlayers = array;
[array release];
}
UIApplication *app = [UIApplication sharedApplication];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(applicationWillTerminate:) name:UIApplicationWillTerminateNotification object:app];
[super viewDidLoad];
}

Answer 1

I don't know plist. But you can try use NSData
NSArray *array;
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];
//Write data
[data writeToFile:filePath atomically:YES];
//Read data
NSFileManager *fileManager = [NSFileManager defaultManager];
NSData *oldData = [fileManager contentsAtPath:filePath];
NSArray *newArray = [NSKeyedUnarchiver unarchiveObjectWithData:oldData]

Answer 2

Welcome to the world of iOS programming. It's a lot of fun, but it can be frustrating, just as programming in any language can be. I feel your pain.
There are a number of things that I see:
In viewDidLoad, it appears that your code to read your file into an array is okay, but then it appears as if you're trying to assign only the first row of this array to your listOfPlayers. Try:
self.listOfPlayers = array;
array is an array, and so is your listOfPlayers. Also, using self will ensure that the synthesized setter is used, thus retaining your listOfPlayers when you release array.
In applicationWillTerminate, I believe you wish to write your listOfPlayers to a file, but what you are actually doing is allocating and initializing an empty array, and writing THAT to your file. Try:
-(void)applicationWillTerminate:(NSNotification*)notification
{
[self.listOfPlayers writeToFile: [self pathOfFile] atomically:YES];
}
I hope this helps!

Answer 3

There seems something wrong in your viewDidLoad
if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {
NSArray *array = [[NSArray alloc]initWithContentsOfFile:filePath];
listOfPlayers.array = [array objectAtIndex:0];
.
.
}
.
.
.
listOfPlayers = [[NSMutableArray alloc] init];
You are accessing listOfPlayers before ever allocating it.
listOfPlayers.array is wrong as well