尝试将数组数据保存/加载到 Plist

Question

我一直在逐步学习 Objective C 和 iPhone SDK，我目前的项目涉及构建一个存储数字数据（体育数据）的应用程序。这主要是出于学习目的，因为有多个应用程序可以做同样的事情。无论如何，我遇到了一些障碍。我的意图是将玩家列表存储在表格中，并允许用户添加其他玩家。

目前，我有一个按钮，当按下时，“忍者”将被添加到表格中。我还启用了在表中删除。不幸的是，我似乎无法弄清楚如何从 plist 中保存和加载数据。我遵循了各种教程和指南，但我无法弄清楚发生了什么。我怀疑我正在从一个空数组加载数据并添加到该数组，但涉及数据的数组是与 plist 不同的数组。不幸的是，除此之外我有点迷失了。

每当我切换视图时，我的数组中的数据都会被删除。但是，我注意到如果我离开并回来，数据仍然存在，但如果我离开相当长的时间，离开并重新启动 iphone 等，数据仍然存在。即使对于我没有使用过的应用程序，这似乎也会发生保存。这只是 iPhone 保留数据以防用户意外退出程序的功能吗？

希望我有点具体地解释了我的问题。 TL:DR 版本：我想将数据添加到数组中，将其保存到 plist，并在屏幕上出现数组时从 plist 重新加载数据。下面的代码试图实现这一点，但没有成功。

谢谢

#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

12 月 20 日代码更新：

-(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

我不知道 plist。不过你可以试试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

欢迎来到 iOS 编程世界。这很有趣，但也可能令人沮丧，就像任何语言的编程一样。我感觉到你的痛苦。

我看到了很多东西：

1. 在 viewDidLoad 中，您将文件读入数组的代码似乎没问题，但看起来好像您只是试图将该数组的第一行分配给您的 listOfPlayers。试试：

   self.listOfPlayers = array;
   

2. array 是一个数组，您的 listOfPlayers 也是如此。此外，使用 self 将确保使用合成的 setter，从而在您释放数组时保留您的 listOfPlayers。

3. 在 applicationWillTerminate 中，我相信您希望将 listOfPlayers 写入文件，但您实际上正在做的是分配和初始化一个空数组，并将其写入您的文件。试试：

   -(void)applicationWillTerminate:(NSNotification*)notification
   {
       [self.listOfPlayers writeToFile: [self pathOfFile] atomically:YES];
   }
   

我希望这会有所帮助！

Answer 3

您的 viewDidLoad 似乎有问题

if ([[NSFileManager defaultManager]fileExistsAtPath:filePath]) {
    NSArray *array = [[NSArray alloc]initWithContentsOfFile:filePath];
    listOfPlayers.array = [array objectAtIndex:0];
    .
    .

}
.
.
.
listOfPlayers = [[NSMutableArray alloc] init];

您在分配之前访问 listOfPlayers。 listOfPlayers.array 也是错误的