Comment dois-je analyser JSON avec Objective-C?

Question

Je suis nouveau à l'iPhone. Quelqu'un peut me dire les étapes à suivre pour analyser ces données et obtenir les détails de l'activité, prénom et nom de famille?

{
    "#error": false, 
    "#data": {
        "": {
            "activity_id": "35336", 
            "user_id": "1", 
            "user_first_name": "Chandra Bhusan", 
            "user_last_name": "Pandey", 
            "time": "1300870420", 
            "activity_details": "Good\n", 
            "activity_type": "status_update", 
            "photo_url": "http://184.73.155.44/hcl-meme/QA_TEST/sites/default/files/pictures/picture-1627435117.jpg"
        }, 
        "boolean": "1", 
        "1": {
            "1": {
                "photo_1_id": "9755"
            }, 
            "activity_id": "35294", 
            "album_name": "Kalai_new_Gallery", 
            "user_id": "31", 
            "album_id": "9754", 
            "user_first_name": "Kalaiyarasan", 
            "user_last_name": "Balu", 
            "0": {
                "photo_0_id": "9756"
            }, 
            "time": "1300365758", 
            "activity_type": "photo_upload", 
            "photo_url": "http://184.73.155.44/hcl-meme/QA_TEST/"
        }, 
        "3": {
            "activity_id": "35289", 
            "user_id": "33", 
            "user_first_name": "Girija", 
            "user_last_name": "S", 
            "time": "1300279636", 
            "activity_details": "girija Again\n", 
            "activity_type": "status_update", 
            "photo_url": "http://184.73.155.44/hcl-meme/QA_TEST/sites/default/files/pictures/picture-33-6361851323080768.jpg"
        }, 
        "2": {
            "owner_first_name": "Girija", 
            "activity_id": "35290", 
            "activity_details": "a:2:{s:4:\"html\";s:51:\"!user_fullname and !friend_fullname are now friends\";s:4:\"type\";s:10:\"friend_add\";}", 
            "activity_type": "friend accept", 
            "owner_last_name": "S", 
            "time": "1300280400", 
            "photo_url": "http://184.73.155.44/hcl-meme/QA_TEST/sites/default/files/pictures/picture-33-6361851323080768.jpg", 
            "owner_id": "33"
        }, 
        "4": {
            "activity_id": "35288", 
            "user_id": "33", 
            "user_first_name": "Girija", 
            "user_last_name": "S", 
            "time": "1300279530", 
            "activity_details": "girija from mobile\n", 
            "activity_type": "status_update", 
            "photo_url": "http://184.73.155.44/hcl-meme/QA_TEST/sites/default/files/pictures/picture-33-6361851323080768.jpg"
        }
    }
}

Answer 1

Avec la perspective de l'OS X v10.7 et iOS 5 lance, probablement la première chose à recommander maintenant, est - NSJSONSerialization, Apple fourni parser JSON. L'utilisation à des tiers seulement comme une solution de secours si vous trouvez que la classe indisponible au moment de l'exécution.

Ainsi, par exemple:

NSData *returnedData = ...JSON data, probably from a web request...

// probably check here that returnedData isn't nil; attempting
// NSJSONSerialization with nil data raises an exception, and who
// knows how your third-party library intends to react?

if(NSClassFromString(@"NSJSONSerialization"))
{
    NSError *error = nil;
    id object = [NSJSONSerialization
                      JSONObjectWithData:returnedData
                      options:0
                      error:&error];

    if(error) { /* JSON was malformed, act appropriately here */ }

    // the originating poster wants to deal with dictionaries;
    // assuming you do too then something like this is the first
    // validation step:
    if([object isKindOfClass:[NSDictionary class]])
    {
        NSDictionary *results = object;
        /* proceed with results as you like; the assignment to
        an explicit NSDictionary * is artificial step to get 
        compile-time checking from here on down (and better autocompletion
        when editing). You could have just made object an NSDictionary *
        in the first place but stylistically you might prefer to keep
        the question of type open until it's confirmed */
    }
    else
    {
        /* there's no guarantee that the outermost object in a JSON
        packet will be a dictionary; if we get here then it wasn't,
        so 'object' shouldn't be treated as an NSDictionary; probably
        you need to report a suitable error condition */
    }
}
else
{
    // the user is using iOS 4; we'll need to use a third-party solution.
    // If you don't intend to support iOS 4 then get rid of this entire
    // conditional and just jump straight to
    // NSError *error = nil;
    // [NSJSONSerialization JSONObjectWithData:...
}

Answer 2

Ne pas réinventer la roue. L'utilisation de json-cadre ou quelque chose de similaire.

Si vous décidez de l'utiliser json-cadre, voici comment analyser une chaîne JSON en NSDictionary:

SBJsonParser* parser = [[[SBJsonParser alloc] init] autorelease];
// assuming jsonString is your JSON string...
NSDictionary* myDict = [parser objectWithString:jsonString];

// now you can grab data out of the dictionary using objectForKey or another dictionary method

Answer 3

1. Je recommande et utiliser TouchJSON pour l'analyse JSON.

2. Pour répondre à votre commentaire d'Alex. Voici rapide code qui devrait vous permettre d'obtenir les champs comme activity_details, nom, etc. à partir du dictionnaire json renvoyé:

   NSDictionary *userinfo=[jsondic valueforKey:@"#data"];
   NSDictionary *user;
   NSInteger i = 0;
   NSString *skey;
   if(userinfo != nil){
       for( i = 0; i < [userinfo count]; i++ ) {
           if(i)
               skey = [NSString stringWithFormat:@"%d",i];
           else
               skey = @"";
   
           user = [userinfo objectForKey:skey];
           NSLog(@"activity_details:%@",[user objectForKey:@"activity_details"]);
           NSLog(@"last_name:%@",[user objectForKey:@"last_name"]);
           NSLog(@"first_name:%@",[user objectForKey:@"first_name"]);
           NSLog(@"photo_url:%@",[user objectForKey:@"photo_url"]);
       }
   }