尝试将.plist中的BOOL值存储到实现文件中的BOOL变量时崩溃

Question

我使用以下代码(MyAppTableViewController)在应用程序启动时创建了一个.plist：

NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *finalPath = [documentsDirectory stringByAppendingPathComponent:@"Settings.plist"];

BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:finalPath];

if (!fileExists) {
    NSLog(@"Creating file");
    NSDictionary *plistDict = [[NSDictionary alloc]initWithObjectsAndKeys:@"1",@"Fade out",@"1",@"Enable Gestures",@"1",@"Proximity Sensor",@"1",@"Keep screen ON",nil];
    NSString *error = nil;

    NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

    if(plistDict) {
        [plistData writeToFile:finalPath atomically:YES];
    } else {
        NSLog(@"Error: %@", error);
        [error release];
    }
}

这可以很好地工作，并且文件是使用键和值创建的。然后，我有一个包含四个开关的表，其中的选择器是函数toggle:。

-(void)toggle:(id)sender中的代码将开关的值与indexPath的行一起获取，并相应地修改plist：

-(void)toggle:(id)sender {
    UISwitch *aSwitch = (UISwitch *)sender;
    UITableViewCell *cell = (UITableViewCell *)aSwitch.superview;
    NSIndexPath *indexPath = [self.tableView indexPathForCell:cell];    

    NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *finalPath = [documentsDirectory stringByAppendingPathComponent:@"Settings.plist"];
    NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithContentsOfFile:finalPath];

    if (indexPath.section == 0 && indexPath.row == 0) {
        [dictionary setObject:[NSNumber numberWithBool:aSwitch.on] forKey:@"Fade out"];
    }
//There are further (similar) else if statements, but I'll leave them out.

    NSString *error = nil;
    NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:dictionary format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

    if(dictionary) {
        [plistData writeToFile:finalPath atomically:YES];
    } else {
        NSLog(@"Error: %@", error);
        [error release];
    }
}

这也工作得很好，并且成功地修改了plist。当我尝试用以下代码检索数据时，我的问题就出现了：

NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *finalPath = [documentsDirectory stringByAppendingPathComponent:@"Settings.plist"];
NSMutableDictionary *dictionary = [NSMutableDictionary dictionaryWithContentsOfFile:finalPath];

fadeOut = [[NSString stringWithFormat:[dictionary objectForKey:@"Fade out"]]boolValue];
proximitySensor = [[NSString stringWithFormat:[dictionary objectForKey:@"Proximity Sensor"]]boolValue];
enableGestures = [[NSString stringWithFormat:[dictionary objectForKey:@"Enable Gestures"]]boolValue];
keepScreenOn = [[NSString stringWithFormat:[dictionary objectForKey:@"Keep screen ON"]]boolValue];

在声明文件中，我定义了BOOL fadeOut,proximitySensor,enableGestures,keepScreenOn;。抓取信息运行良好，但当我更改BOOL值时，应用程序崩溃。我不太明白问题出在哪里。也许我错过了更大的图景，或者布尔值的一个简单但重要的错误。

如果我删除上面的代码，一切都会正常工作。但如果我把它放在那里，应用程序就会崩溃，并显示以下消息：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFBoolean length]: unrecognized selector sent to instance 0x3f39a9f0'

非常感谢您的帮助！

Answer 1

如果你看这条线

fadeOut = [[NSString stringWithFormat:[dictionary objectForKey:@"Fade out"]]boolValue]

您正在从NSNumber初始化一个字符串(您将您的BOOL存储在一个NSNumber中)。这本身就是无效的。

如果需要NSNumber的布尔值，只需对其使用boolValue即可。

fadeOut = [[dictionary objectForKey:@"Fade out"] boolValue];

这对于检索布尔值的所有时间都是正确的。