Saving and retrieving information on device - ios

Question

This is a simple project that I am half copying from a book to teach myself. It's a to do list, with a table view, a text field and a button to add the task to the list. Then it saves the array of tasks to a directory (using a helper function) and when you close and reopen the application it retrieves the information. The thing runs on the computer and I thought it also worked on the device until I closed the app and reopened it to discover none of the elements of the array where there. As it works on the computer I have no idea what isn't right. Some of this code I understand, some I just copied for now (like the helper function), any suggestions greatly appreciated! P
Code:
h file
#import <UIKit/UIKit.h>
NSString *docPath();
#interface ViewController : UIViewController<UITableViewDataSource>
{
UITableView *taskTable;
UITextField *taskField;
UIButton *insertButton;
NSMutableArray *tasks;
}
- (void)addTask:(id)sender;
- (void)writeTasksToFile:(NSString *)path;
#end
m file
#import "ViewController.h"
NSString *docPath()
{
NSArray *pathList = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
return [[pathList objectAtIndex:0] stringByAppendingString:#"data.td"];
}
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSArray *plist = [NSArray arrayWithContentsOfFile:docPath()];
if(plist) {
tasks = [plist mutableCopy];
} else {
tasks = [[NSMutableArray alloc] init];
}
CGRect buttonFrame = CGRectMake(228,40,72,31);
insertButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[insertButton setFrame:buttonFrame];
insertButton.backgroundColor = [UIColor redColor];
[insertButton addTarget:self action:#selector(addTask:) forControlEvents:UIControlEventTouchUpInside];
[insertButton setTitle:#"Insert" forState:UIControlStateNormal];
[[self view] addSubview:insertButton];
CGRect tableFrame = CGRectMake(0, 80, 320, 380);
taskTable = [[UITableView alloc] initWithFrame:tableFrame style:UITableViewStylePlain];
[taskTable setSeparatorStyle:UITableViewCellSeparatorStyleNone];
taskTable.separatorStyle = UITableViewCellSeparatorStyleSingleLine;
[self.view addSubview:taskTable];
[taskTable setDataSource:self];
CGRect fieldFrame = CGRectMake(20, 40, 200, 31);
taskField = [[UITextField alloc]initWithFrame:fieldFrame];
[taskField setBorderStyle:UITextBorderStyleRoundedRect];
[taskField setPlaceholder:#"type a task, enter"];
[taskField setBackgroundColor:[UIColor greenColor]];
[self.view addSubview:taskField];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(applicationDidEnterBackground:) name:UIApplicationDidEnterBackgroundNotification object:nil];
}
- (void) applicationDidEnterBackground:(UIApplication *)application {
[tasks writeToFile:docPath() atomically:YES];
}
- (void)addTask:(id)sender{
NSString *t = [taskField text];
if ([t isEqualToString:#""]) {return;}
[tasks addObject:t];
[taskTable reloadData];
[taskField setText:#""];
[taskField resignFirstResponder];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{
return [tasks count];
}
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete)
{
[tasks removeObjectAtIndex:indexPath.row];
[tableView deleteRowsAtIndexPaths:#[indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}
}
-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{
UITableViewCell *c = [taskTable dequeueReusableCellWithIdentifier:#"Cell"];
if (!c){
c = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"Cell"];
}
NSString *item = [tasks objectAtIndex:[indexPath row]];
[[c textLabel] setText:item];
return c;
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)writeTasksToFile:(NSString *)path
{
[tasks writeToFile:path atomically:YES];
}
#end
edit------------------------------------------------------------------------------------------------------------------------------
Here is a debugger screenshot with a break point on the line that checks to see if there is a plist.

Answer 1

One thing I see that needs to be changed is that your docPath() is returning a bad path. You need to use stringByAppendingPathComponent instead of stringByAppendingString
return [[pathList objectAtIndex:0] stringByAppendingPathComponent:#"data.td"];
Or, if you want to use stringByAppendingString then it should be:
return [[pathList objectAtIndex:0] stringByAppendingString:#"/data.td"];