Need help for parsing JSON - iphone

Question

I'm learning how to parse JSON. I've made the raywenderlich tutorial but I'm still lost with some steps. I got my own JSON :
{
"Albumvideo":{
"album01":{
"titreAlbum":"Publicité",
"photoAlbum":"blabla.jpg",
"pubVideos":{
"pub01":[
{
"titrePub":"Chauffage Compris",
"dureePub":"01'25''",
"photoPub":"chauffage.jpg",
"lienPub":"http://www.wmstudio.ch/videos/chauffage.mp4"
}
]
}
},
"album02":{
"titreAlbum":"Events",
"photoAlbum":"bloublou.jpg",
"eventsVideos":{
"event01":[
{
"titreEvent":"Chauffage Compris",
"dureeEvent":"01'25''",
"photoEvent":"chauffage.jpg",
"lienEvent":"http://www.wmstudio.ch/videos/chauffage.mp4"
}
]
}
}
}
}
The I got my 'Code' to parse my JSON :
- (void) viewDidLoad
{
[super viewDidLoad];
dispatch_async (kBgQueue, ^{
NSData* data = [NSData dataWithContentsOfURL:lienAlbumsVideo];
[self performSelectorOnMainThread:#selector(fetchedData:)withObject:data waitUntilDone:YES];
});
}
- (void)fetchedData:(NSData *)responseData {
//parse out the json data
NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
NSArray* albumsVideo = [json objectForKey:#"Albumvideo"];
NSLog(#"Nombre d'albums : %i",[albumsVideo count]);
}
This works fine, my NSLog returns '2'. Where I now have difficulties is to make an array with "titreAlbum" or "event01" for example. If I do :
NSArray* event01 = [json objectForKey:#"event01"];
NSLog(#"Number of objects in event01 : %i ", [event01 count]);
My NSLog returns '0'.
I didn't really understand how to parse information from multidimensional array in a JSON. Thank's already!
Nicolas

Answer 1

You do not have a two-dimensional array. And JSON does not support this, but arrays of array (as C does and as Objective-C does).
NSDictionary *document = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];
// Getting titreAlbum
NSDictionary *albumVideo = document[#"Albumvideo"];
NSDictionary *album01 = albumVideo[#"album01"];
NSString *titreAlbum = album01[#"titreAlbum"];
// Getting an event
NSDictionary *album02 = albumVideo[#"album02"];
NSDictionary *eventVideos = album02[#"eventsVideos"];
NSArray *event01 = eventVideo[#"event01"];
(Typped in Safari)
You can use KVC, too, if you are not interested in the middle layers.
But your identifiers and question let me think, that the structure of your JSON is malformed.

Answer 2

Some things,
every time you see
{ ... }
in the json that is the beginning/end of an NSDictionary
once parsed, while
[ ... ]
is the beginning end of an NSArray.
So once you parse the json using NSJSONSerialization you can navigate that dictionary using that knowledge.
Given the json you have to get an array of "titreAlbum" you would have to do something like:
NSDictionary *albumVideo = json[#"Albumvideo"];
NSMutableArray *albumTitres = [[NSMutableArray alloc] init];
for (NSDictionary *album in albumVideo) {
[albumTitres addObject:album[#"titreAlbum"]];
}
That said, I think your json is not malformed as is passing the JSONLint validation, but is not helping you to parse it. I would expect that the Albumvideo is an array of albums, instead of a dictionary of albums.

Answer 3

I had the same issue. I was actually trying to access Google Distance API where i needed to get
{
"routes" : [
{
"bounds" : {
"northeast" : {
"lat" : 23.0225066,
"lng" : 73.2544778
},
"southwest" : {
"lat" : 19.0718263,
"lng" : 72.57129549999999
}
},
"copyrights" : "Map data ©2014 Google",
"legs" : [
{
"distance" : {
"text" : "524 km",
"value" : 523839
},
"duration" : {
"text" : "7 hours 34 mins",
"value" : 27222
},
"end_address" : "Mumbai, Maharashtra, India",
"end_location" : {
"lat" : 19.0759856,
"lng" : 72.8776573
},
"start_address" : "Ahmedabad, Gujarat, India",
"start_location" : {
"lat" : 23.0225066,
"lng" : 72.57129549999999
},
"steps" : [
{
"distance" : {
"text" : "0.2 km",
"value" : 210
},
"duration" : {
"text" : "1 min",
"value" : 25
},
"end_location" : {
"lat" : 23.0226436,
"lng" : 72.573224
},
"html_instructions" : "Head on Swami Vivekananda RdRoad/Swami Vivekananda Rd",
"polyline" : {
"points" : "uqokCsa}yLS?GYEk#Cq##qA#eA#aADm#"
},
"start_location" : {
"lat" : 23.0225066,
"lng" : 72.57129549999999
},
"travel_mode" : "DRIVING"
}]`
I needed to access routes.legs.steps.html_instructions.
So my code is as under
NSURL *url=[[NSURL alloc] initWithString:[NSString stringWithFormat:#"http://maps.googleapis.com/maps/api/directions/json?origin=ahmedabad&destination=%#",self.city]];`
NSURLResponse *res;
NSError *err;
NSData *data=[NSURLConnection sendSynchronousRequest:[[NSURLRequest alloc] initWithURL:url] returningResponse:&res error:&err];
NSDictionary *dic=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
NSArray *routes=dic[#"routes"];
NSArray *legs=routes[0][#"legs"];
NSArray *steps=legs[0][#"steps"];
NSMutableArray *textsteps=[[NSMutableArray alloc] init];
NSMutableArray *latlong=[[NSMutableArray alloc]init];
for(int i=0; i< [steps count]; i++){
NSString *html=steps[i][#"html_instructions"];
[latlong addObject:steps[i][#"end_location"]];
[textsteps addObject:html];
}