How to iterate through a simple JSON object in Objective-C? - objective-c

Question

I'm very new to Objective-C, I'm a hardcore Java and Python veteran.
I've created an Objective-C script that calls a URL and gets the JSON object returned by the URL:
// Prepare the link that is going to be used on the GET request
NSURL * url = [[NSURL alloc] initWithString:#"http://domfa.de/google_nice/-122x1561692/37x4451198/"];
// Prepare the request object
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url
cachePolicy:NSURLRequestReturnCacheDataElseLoad
timeoutInterval:30];
// Prepare the variables for the JSON response
NSData *urlData;
NSURLResponse *response;
NSError *error;
// Make synchronous request
urlData = [NSURLConnection sendSynchronousRequest:urlRequest
returningResponse:&response
error:&error];
// Construct a Array around the Data from the response
NSArray* object = [NSJSONSerialization
JSONObjectWithData:urlData
options:0
error:&error];
//NSLog(object);
// Iterate through the object and print desired results
I've gotten this far:
NSString* myString = [#([object count]) stringValue];
NSLog(myString);
Which returns the size of this array, but how can I loop through this JSON object and print each element?
Here's the JSON I'm loading:
{
"country": "United States",
"sublocality_level_1": "",
"neighborhood": "University South",
"administrative_area_level_2": "Santa Clara County",
"administrative_area_level_1": "California",
"locality": "City of Palo Alto",
"administrative_area_level_3": "",
"sublocality_level_2": "",
"sublocality_level_3": "",
"sublocality":""
}

Answer 1

The top-level object your JSON object is a dictionary, not an array, as indicated by the curly braces. If you are not sure whether you are going to get an array or a dictionary back, you can do some safety checking like this:
// Construct a collection object around the Data from the response
id collection = [NSJSONSerialization JSONObjectWithData:urlData
options:0
error:&error];
if ( collection ) {
if ( [collection isKindOfClass:[NSDictionary class]] ) {
// do dictionary things
for ( NSString *key in [collection allKeys] ) {
NSLog(#"%#: %#", key, collection[key]);
}
}
else if ( [collection isKindOfClass:[NSArray class]] ) {
// do array things
for ( id object in collection ) {
NSLog(#"%#", object);
}
}
}
else {
NSLog(#"Error serializing JSON: %#", error);
}

Answer 2

Well for starters, the JSON you linked to is not an array, it is a dictionary.
NSDictionary* object = [NSJSONSerialization
JSONObjectWithData:urlData
options:0
error:&error];
There are a number of ways to iterate through all of the keys/values, and here is one:
for(NSString *key in [object allKeys])
{
NSString *value = object[key]; // assuming the value is indeed a string
}