从NSDictionary对象的NSArray中，如何获取唯一的NSArray

Question

I'm writing an app that deals with Albums of pictures.

I have the following JSON document which lists Albums.

{
  "Albums": [
    {
      "id": 1234,
      "Title": "My Birthday 2008",
      "Category": {
        "id": 0,
        "Name": "Birthdays"
      }
    },
    {
      "id": 5678,
      "Title": "Disneyland Trip 2010"
      "Category": {
        "id": 1,
        "Name": "Trips"
      },
    }
  ]
}

As you can see, Albums reside in Categories.

I've used NSJSONSerialization class to bring this into an NSDictionary object which contains an NSArray of NSDictionaries (per the "schema" of the above JSON).

From this, I want to generate an NSArray of unique Categories NSDictionary objects. Something like:

{
  "Categories": [
    {
      "id": 0,
      "Name" : "Birthdays"
    },
    {
      "id": 1,
      "Name" : "Trips"
    },
  ]
}

Scouring stackoverflow, I've found some things that seem like good building blocks

categories = [albums valueForKeyPath:@"@distinctUnionOfObjects.Category.Name"];

but that obviously only generates an NSArray of NSStrings. What I want is it to be an NSArray of NSDictionaries which has two objects in it with keys "id" and "Name". I can't seem to put it all together to get what I want, without the poorman/brute method of nested if loops. I guess I'm looking for some utility method for the NSDictionary or NSArray classes that can help me do this faster.

Any help is appreciated, thanks.

Answer 1

Why not just use the JSON parser? It should give you what you want.

http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html