iPhone：变量范围问题

Question

我使用此代码从 plist 加载数据。

-(void)loadOrCreateData {
    NSLog(@"Start loadOrCreateData");
    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) 
    {
        NSLog(@"File Exists.. Loading from plist File");
        NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
        font = [array objectAtIndex:0];
        background = (NSString *)[array objectAtIndex:1];
        animation = [array objectAtIndex:5];
        [array release];
        NSLog(@"Loading Done!");
    }
    else 
    {
        NSLog(@"File does not exist.. Creating new plist File");
        font = @"Georgia-BoldItalic";
        background = @"monalisa.jpeg";
        animation = @"103";
        [self saveData];
    }

    NSLog(@"Finish loadOrCreateData");
}

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

- (void)saveData {
   NSMutableArray *array = [[NSMutableArray alloc] init];
   [array addObject:font];
   [array addObject:background];
   [array addObject:animation];
   [array writeToFile:[self dataFilePath] atomically:YES];
   [array release];
}

当没有可从中获取数据的 plist 文件时，第一次一切加载正常。但在第二次加载时，当我尝试在 loadOrCreate 方法之外使用加载的数据时，应用程序崩溃了。由于某种原因，在 loadOrCreate 方法外部访问时，字体、背景和动画中的数据不可用。变量 - 字体、背景和动画在 .h 文件中声明为 NSString，因此应该全局可用，对吗？您能告诉我这是什么原因吗？

Answer 1

您必须保留该对象。

    font = [[array objectAtIndex:0] retain];
    background = (NSString *)[[array objectAtIndex:1] retain];
    animation = [[array objectAtIndex:5] retain];
...
    font = [@"Georgia-BoldItalic" retain];
    background = [@"monalisa.jpeg" retain];
    animation = [@"103" retain];

注意：如果您多次加载数据，请不要忘记在设置值之前释放它们。

编辑：

-(void)loadOrCreateData {
    [font release];
    [background release];
    [animation release];

    NSLog(@"Start loadOrCreateData");
    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) 
    {
        NSLog(@"File Exists.. Loading from plist File");
        NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
        font = [[array objectAtIndex:0] retain];
        background = (NSString *)[[array objectAtIndex:1] retain];
        animation = [[array objectAtIndex:5] retain];
        [array release];
        NSLog(@"Loading Done!");
    }
    else 
    {
        NSLog(@"File does not exist.. Creating new plist File");
        font = [@"Georgia-BoldItalic" retain];
        background = [@"monalisa.jpeg" retain];
        animation = [@"103" retain];
        [self saveData];
    }

    NSLog(@"Finish loadOrCreateData");
}