对象数 (0) 与键数 (1) 不同

Question

不断弹出一个错误，提示键的数量与对象的数量不同，并且程序不断崩溃。

下面的代码是有问题的。

-(void)saveData //error is in here
{

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
//get documents path
NSString *documentsPath = [paths objectAtIndex:0];
//get the path to our Data/plist file
NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"Data.plist"];

//set the variables to the values in the text fields
self.topScores = highScore.text;

//create dictionary with values in UITextFields
NSDictionary *plistDict = [NSDictionary dictionaryWithObjects: [NSArray arrayWithObjects: topScores, nil] forKeys:[NSArray arrayWithObjects: @"bestScore", nil]];

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

//check if plist data exists
if (plistData)
{
    //write plistData to our Data.plist file
    [plistData writeToFile:plistPath atomically:YES];
}
else
{
    NSLog(@"Error in saveData: %@", error);
    [error release];
 }
}

代码可以运行，但在此处崩溃

         if (newTopScore > [topScores intValue]) 
        {
            topScores = ([NSString stringWithFormat:@"%i", newTopScore]); 
        }

        highScore.alpha = 1; 

    [self saveData];

Answer 1

一定是这一行：

NSDictionary *plistDict = [NSDictionary dictionaryWithObjects: [NSArray arrayWithObjects: topScores, nil] forKeys:[NSArray arrayWithObjects: @"bestScore", nil]];

而且一定是topScores 为 nil，表示 objects 数组的大小为 0，而 keys 数组的大小为 1。

您需要找出为什么topScores 为零。

例如，尝试运行以下代码：

NSDictionary *plistDict = [NSDictionary dictionaryWithObjects:@[] 
                                                      forKeys:@[@"bestScore"]];

你会得到：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSDictionary initWithObjects:forKeys:]: count of objects (0) differs from count of keys (1)'