Question

我正在开发我的第一个iphone'Diary'应用程序，它使用自定义'Entry'对象，其中包含NSString标题，NSString文本和NSDate creationDate。当我尝试存档Entry对象的NSMutableArray，并在下次加载视图时检索它们时，应用程序崩溃。我已经浏览了一堆使用NSKeyedArchivers的示例代码和示例，但仍然无法弄清楚为什么会发生这种情况。我猜测数据的初始化有一个问题，它保存条目但不确定......

这是代码，也许你可以找到我持续监督的东西......“

//--------- Entry.m---------------

- (id) initWithCoder:(NSCoder *)aDecoder{

if ((self = [super init])) {
    self.title = [[aDecoder decodeObjectForKey:@"title"] retain];
    self.text = [[aDecoder decodeObjectForKey:@"text"] retain];
    self.created = [[aDecoder decodeObjectForKey:@"created"] retain];
}
return self;

}

- (void) encodeWithCoder:(NSCoder *)aCoder{

[aCoder encodeObject:self.title forKey:@"title"];
[aCoder encodeObject:self.text forKey:@"text"];
[aCoder encodeObject:self.created forKey:@"created"];

}

//-------------- Diary View Controller.m

- (NSString *)dataFilePath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, 
     NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
return [documentsDirectory stringByAppendingPathComponent:kFilename];
}

- (void) writeDataToArchive {
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]
                             initForWritingWithMutableData:data];

[archiver encodeObject:self.entriesArray forKey:@"entriesArray"];
[archiver finishEncoding];
BOOL result = [data writeToFile:[self dataFilePath]  atomically:YES];
[archiver release];
[data release];    
}

- (void)addItem:sender {
int count = [entriesArray count] +1;    
NSString *newEntryTitle = [NSString stringWithFormat:@"Entry %d", count];    
Entry *anEntry = [[Entry alloc] initWithTitle:newEntryTitle text:@"-" 
         created:[NSDate date]];
[entriesArray addObject:anEntry];
[self.tableView reloadData];

[anEntry release];
[self writeDataToArchive];
}

- (void)viewDidLoad
{
[super viewDidLoad];
NSString *filePath = [self dataFilePath];
if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {     
     NSData *data = [[NSMutableData alloc]
                     initWithContentsOfFile:[self dataFilePath]];

     NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]
          initForReadingWithData:data];
     NSMutableArray *array = [unarchiver decodeObjectForKey:@"entriesArray"];     
     entriesArray = [array mutableCopy];
     [array release];
     [unarchiver finishDecoding];
     [unarchiver release];
     [data release];
}
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:
    (NSIndexPath *)indexPath
{
    // ... some other stuff
     NSUInteger row = indexPath.row;
     Entry *entry = [entriesArray objectAtIndex:row];

     cell.textLabel.text = entry.title;
     return cell;
}

非常感谢。

Answer 1

当您使用NSKeyedUnarchivers读取数组时，您总是会得到一个不可复制的副本。你需要将*数组声明为NSArray，或者只是将数组一起删除。

entriesArray = [[unarchiver decodeObjectForKey:@"entriesArray"] mutableCopy];

@JeremyP指出了另一个问题。由于您没有分配或保留*数组，因此不应将其释放。

Answer 2

您不应在array中发布viewDidLoad，因为您不拥有它。

请查看Cocoa memory management Rules，因为您的代码中存在其他一些内存管理问题。特别是，

self.title = [[aDecoder decodeObjectForKey:@"title"] retain];
self.text = [[aDecoder decodeObjectForKey:@"text"] retain];
self.created = [[aDecoder decodeObjectForKey:@"created"] retain];

在您的initWithCoder:方法中，假设属性被保留或复制，所有泄漏都会泄漏。

当我使用NSKeyedArchivers / NSKeyedUnarchivers时，无法弄清楚为什么我的应用程序崩溃了

2 个答案: