NSDictionary不会将自身保存到.plist文件中

Question

我已经阅读了很多问答，但是他们并没有解决我的问题。

我编写了此方法，将笔尖中的一些数据保存到字典中，然后保存到.plist中

-(void)save{

NSString *saveFilePath = [self saveFilePath];

if ([[NSFileManager defaultManager]fileExistsAtPath:saveFilePath]) {

        NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile:saveFilePath];
        //I Use the "today date" for key
        NSDate *today = [[NSDate alloc]init];
        NSMutableArray *array = [[NSMutableArray alloc]init];
        NSString *delta = [[NSString alloc]initWithFormat:@"%d",[kmNew.text intValue] - [kmOld.text intValue]];

        [array addObject:delta];
        [array addObject:[consumoKg text]];
        [array addObject:[consumoEuro text]];

        [dictionary setObject:array forKey:today];

    BOOL success = [dictionary writeToFile:[self saveFilePath] atomically:YES];
    NSLog(@"%d",success);
        [today release];
        [delta release];
        [array release];
        [dictionary release];
}
else{

    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] init];

    NSDate *today = [[NSDate alloc]init];
    NSMutableArray *array = [[NSMutableArray alloc]init];

    NSString *delta = [[NSString alloc]initWithFormat:@"%d",[kmNew.text intValue] - [kmOld.text intValue]];

    [array addObject:delta];
    [array addObject:[consumoKg text]];
    [array addObject:[consumoEuro text]];

    [dictionary setObject:array forKey:today];

    // Check if the value are store correctly into the dictionary

    for (NSDate *key in dictionary) {
        for (NSString *string in [dictionary objectForKey:key]) {
            NSLog(@"%@",string);
        }
    }

   BOOL success =  [dictionary writeToFile:[self saveFilePath] atomically:YES];
   NSLog(@"%d",success);

    [today release];
    [delta release];
    [array release];
    [dictionary release];
}
}

saveFilePath方法如下：

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

变量已正确存储到字典中，但BOOL返回值“成功”为0。为什么？

Answer 1

我猜NSDictionary键必须是字符串。 保存到plist文件时，不允许使用NSDate。