cocoa - 将 NSMutableDictonary 添加到 NSMutableArray 但对象被替换

Question

为什么每当我向 NSMutableArray 添加一个新对象 NSMutableDictionay 时，它就会替换我以前的对象？

例如:

[appDelegate.tracksDict setObject:currentTrackTitle forKey:@"track_title"];
[appDelegate.tracksDict setObject:currentTrackTopic forKey:@"topic"];
[appDelegate.tracksArray addObject:[appDelegate.tracksDict copy]];

正在打印...

2010-10-01 14:03:35.021 XML[48889:207]Tracks Array: {
    topic = "Cold Calling";
    "track_title" = "Sleeping and selling";
}
2010-10-01 14:03:35.021 XML[48889:207]Tracks Array: {
    topic = "Gate Keeper";
    "track_title" = "Selling like a chicken";
}
2010-10-01 14:03:35.021 XML[48889:207]Tracks Array: {
    topic = "Gate Keeper";
    "track_title" = "Don't you try to sell";
}

而不是像...

2010-10-01 14:03:35.021 XML[48889:207]Tracks Array: {
    topic = "Cold Calling";
    track_title = "Sleeping and selling";

    topic = "Gate Keeper";
    track_title = "Selling like a chicken";

    topic = "Gate Keeper";
    track_title = "Selling like a chicken";
}

我确信这很愚蠢，因为我不太了解这种语言。

Answer 1

根据您发布的“打印”，您的问题很难理解，但听起来您想要一个 NSDictionary 对象的 NSArray 。 NSDictionary 只能保存给定键的单个对象，但可以拥有(实际上)无限的键。看起来您需要的是构建一组字典，每个轨道一个。