iPhone:变量范围问题

时间:2011-02-18 04:00:00

标签: iphone plist scope

我已经使用此代码从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plist文件从中获取数据时,第一次正常加载。但是在第二次加载时,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。出于某种原因,在loadOrCreate方法之外访问时,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NSStrings,因此应该是全局可用的吗?你能告诉我这是什么原因吗?

1 个答案:

答案 0 :(得分:2)

您必须保留这些对象。

    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,请不要忘记在设置之前释放值。

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");
}