Objective c 为什么我的[dictionary objectForKey:@“TOSAcceptedValue”为空？

我正在向我的文档目录中的plist写入和读取数据。首先，如果没有找到文件，我就把文件写出来。这似乎工作正常，因为起初那里没有文件，现在有了，双击该文件会显示名为

toAcceptedValue

的键的预期内容，该键的值为no

但是如果文件被找到了，这发生在我运行上面一次之后，我尝试读取相同的值，我得到一个空值。这是代码，它可能不好看，因为我已经在黑客一段时间，让它的功能

NSError *error;
NSString *TOSAcceptedStatus ;

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSLog( @"paths is %@", paths);

NSString *documentsDirectory = [paths objectAtIndex:0]; 
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"AppUsage.plist"];

NSFileManager *fileManager = [NSFileManager defaultManager];

//first see if file exists. if it doesn't then write it out with a value of NO for Terms of Use Accepted
if (![fileManager fileExistsAtPath: path])
{                
    NSMutableDictionary *appUsageNo = [[NSMutableDictionary alloc] initWithContentsOfFile: path];

    //here add element to data file and write data to file
    NSString *value = @"NO";

    [appUsageNo setObject:@"TOSAcceptedValue" forKey:value];

    [appUsageNo writeToFile: path atomically:YES];
    [appUsageNo release]; 

    //and set TOSAcceptedStatus to no since we know its a no right now
    TOSAcceptedStatus = @"NO";

}
else { //file was found at expected location so let's see if they accepted Terms of Use already

    NSMutableDictionary *dictionary = [[NSMutableDictionary alloc] initWithContentsOfFile: path];
    NSLog( @"path is %@", path);

    TOSAcceptedStatus = [dictionary objectForKey:@"TOSAcceptedValue"];
    //NSLog(@"TOSAcceptedStatus is %@", TOSAcceptedStatus);
    NSLog(@"TOSAcceptedStatus is %@", [dictionary objectForKey:@"TOSAcceptedValue"]);

    [dictionary release];
}

这是我的控制台结果

2011-09-09 21:47:23.177 myApp[1027:207] paths is (
    "/Users/user1/Library/Application Support/iPhone Simulator/4.3/Applications/34562D85-DBE9-4A4F-A142-JEFC1F4808D1/Documents"
)
2011-09-09 21:47:44.915 myApp[1027:207] path is /Users/user1/Library/Application Support/iPhone Simulator/4.3/Applications/34562D85-DBE9-4A4F-A142-JEFC1F4808D1/Documents/AppUsage.plist
2011-09-09 21:47:50.448 myApp[1027:207] TOSAcceptedStatus is (null)

有什么线索可以告诉我为什么我不能返回

到AcceptedStatus

吗

---

另外，在应用程序启动后，是否允许我向plist进行写操作和读操作

我认为您的主要问题是对象和键向后：

[appUsageNo setObject:value forKey:@"TOSAcceptedValue"];

---

[[NSMutableDictionary alloc]dictionaryWithContentsOfFile:path]--这似乎有点荒谬。为什么要创建一本词典，扔掉它，然后再创建第二本呢。如果第二个已经自动释放了，为什么还要释放它呢？在上面的声明中，我肯定有我的键和值。谢谢你能听到。当然，很高兴能为你服务！尝试执行
NSLog（@“%@，[dictionary description]），以查看您得到了什么。“TOSAcceptedValue”可能不在字典中。这与以下代码一样有帮助：for（dictionary中的id key）{NSLog（@“key:%@，value:%@），key，[dictionary objectForKey:key]）；也很有帮助。它帮助我更好地了解了plist的结构。感谢您的帮助。