iphone - 写入 plist 字典中的字符串

Question

我使用的 plist 结构如下:plist, array, dict key string key string/dict, dict key string key string/dict,/array,/plist。

我希望通过以下代码将当前字典中“Done”字符串的值设置为“Yes”。

但是现在，代码用当前字典的字符串替换了整个字典数组(尽管“Done”键的值应该是“Yes”。)

什么是我想要的正确代码？

在 DetailViewController.m 中:

-(IBAction)favoriteButtonPressed:(id)sender
{

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


[[detailsDataSource objectAtIndex: detailIndex] setValue:@"Yes" forKey:@"Done"];
[[detailsDataSource objectAtIndex: detailIndex] writeToFile:path atomically:YES];
}

如果重要的话，detailsDataSource 和 detailIndex 从 TableViewController.m segue 接收。

TableViewController.m segue部分:

    detailViewController.detailsDataSource = [[NSArray alloc]initWithArray:objectsArray];
    detailViewController.detailIndex = selectedRowIndex.row;

DetailViewController viewDidLoad

if ([[[detailsDataSource objectAtIndex: detailIndex] valueForKey:@"Favorite"] isEqual:@"Yes"])  {

    [favoriteButton setImage:[UIImage imageNamed:@"favoritedItem.png"] forState:UIControlStateSelected | UIControlStateHighlighted];
 }


districtLabel.text = [[detailsDataSource objectAtIndex: detailIndex] valueForKey:@"District"];

detailsDataSource 数组在 detailViewController 中是这样使用的，所以我不能从数组更改为字典，在这种情况下必须制作一个可变副本。

Answer 1

setValue:forKey 不用于修改可变字典。您应该使用 setObject:forKey。即，这个:

[[detailsDataSource objectAtIndex: detailIndex] setValue:@"Yes" forKey:@"Done"];

应该是:

[[detailsDataSource objectAtIndex: detailIndex] setObject:@"Yes" forKey:@"Done"];

如果这不能解决问题，请确保字典和数组都是可变的:

-(IBAction)favoriteButtonPressed:(id)sender {

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

    NSMutableDictionary *mutDict = [NSMutableDictionary dictionaryWithDictionary:[detailsDataSource objectAtIndex:detailIndex]];
    [mutDict setObject:@"Yes" forKey:@"Done"];

    NSMutableArray *tmpMutArr = [NSMutableArray arrayWithArray:detailsDataSource];
    [tmpMutArr replaceObjectAtIndex:detailIndex withObject:[NSDictionary dictionaryWithDictionary:mutDict]];  // make dict immutable before replacing.  Casting it ( (NSDictionary *)mutDict ) works too.

    [detailsDataSource release], detailsDataSource = nil;
    detailsDataSource = [[NSArray alloc] initWithArray:tmpMutArr];

    [detailsDataSource writeToFile:path atomically:YES];
}

---

此外，您可以使用[NSNumber numberWithBool:YES]代替@"Yes":
[mutDict setObject:[NSNumber numberWithBool:YES] forKey:@"Done"];
通常使用 @"Yes" 会更好。

和:

districtLabel.text = [[detailsDataSource objectAtIndex: detailIndex] valueForKey:@"Yes"];

应该是:

districtLabel.text = [[detailsDataSource objectAtIndex: detailIndex] objectForKey:@"Yes"];

---

还注意到您可能有内存泄漏:

detailViewController.detailsDataSource = [[NSArray alloc] initWithArray:objectsArray];

确保在使用保留的属性 setter 时自动释放。