ios - 将项目追加到 plist 中保存的 NSDictionary 中的现有键

Question

如何将值从 plist 附加到 NSDictionary 中的现有键？

我所拥有的基本上是一个保存在光盘中的plist，其中包含一些键和值，键是一些具有一个初始值的学生的名字。我想做的不起作用的是通过读取 plist 将更多项目附加到现有键/学生，将其添加到临时 NSDictionary，将临时数组附加到 plist 中的现有键，但是当我保存plist 返回它不起作用，它只保存最后两项，并且基本上删除该键的初始值。

这是我正在使用的代码...

- (IBAction)testing:(id)sender
{
    NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [dirPaths objectAtIndex:0];
    NSString *fullPath = [documentsPath stringByAppendingPathComponent:@"studentsRecords.plist"];

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

    if(fileExists)
    {
        NSMutableDictionary *dictionaryRecords = [[NSMutableDictionary alloc]initWithContentsOfFile:fullPath];
        NSLog(@"Items for Nathan: %@",[dictionaryRecords objectForKey:@"Nathan"]);// here the output is, Items for Nathan: Ruler
        // which make sense since I only had one initial record for Nathan in my plist,

        // Here, I want to add two more items to the key Nathan by appending an arry to
        // NSMutableDictionary (dictionaryRecords) but it doesnt work
        NSArray *tempArray = @[@"NoteBook", @"Pencil"];
        [dictionaryRecords setObject:tempArray forKey:@"Nathan"];

        [dictionaryRecords writeToFile:fullPath atomically:YES];
        // when I check the plist after saving this, I only see the last two values, NoteBook and Pencil
        // instead of the three that I'm expecting, Ruler, NoteBook and Pencil
    }

}

我在这里缺少什么？

提前非常感谢。

Answer 1

[dictionaryRecords setObject:tempArray forKey:@"Nathan"] 用 tempArray 替换之前的值。

如果您想添加到现有数组，您必须检索它，制作一个可变副本，然后追加到它。