iOS JSON Array and MapKit - iphone

Question

I am trying to map a JSON array using the MapKit. I can get a single point on the map with the code below, but I have dozens of pins I need to mark, and I have a JSON array prepared. My code for a single point is below.
In my .h file:
#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#interface MapViewController : UIViewController {
MKMapView *mapView;
NSData *data;
}
#property (nonatomic, retain) IBOutlet MKMapView *mapView;
#end
In my .m file:
NSData *data = #"[{"id":"1","name":"Jiffy Lube","lat":"21.306","lon":"-157.861"},
{"id":"2","name":"Bills
Oil","lat":"21.301","lon":"-157.863"},{"id":"3","name":"Auto Zone","lat":"21.307","lon":"-
157.862"}]";
// parse the JSON into a NSArray
NSError *error;
NSArray *array = [NSJSONSerialization JSONObjectWithData:data
options:0
error:&error];

Answer 1

Your JSON is an array of dictionary items. So you can just retrieve the full array via NSJSONSerialization, and then iterate through the dictionary entries in the resulting array.
First, you originally said you had JSON like the following:
[{"id":"1","name":"Jiffy Lube","lat":"21.306","lon":"-157.861"},
{"id":"2","name":"Bills Oil","lat":"21.301","lon":"-157.863"},
{"id":"3","name":"Auto Zone","lat":"21.307","lon":"-157.862"}]
So, if that's sitting in a file, "test.json" that you've included in your bundle, you could load it as so:
// load the data from local file
NSString *path = [[NSBundle mainBundle] pathForResource:#"test" ofType:#"json"];
NSData *data = [NSData dataWithContentsOfFile:path];
If you have this on a web server, you'd retrieve it like so:
// load the data from web server
NSURL *url = [NSURL URLWithString:#"http://insert.your.server/and/url/here/test.json"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
// use NSData here
}];
Assuming you loaded your JSON feed into a NSData object called data, you could just do something like:
// parse the JSON into a NSArray
NSError *error;
NSArray *array = [NSJSONSerialization JSONObjectWithData:data
options:0
error:&error];
if (error != nil)
{
// handle the error as you want
}
// a few variables to be used as we iterate through the array of results
CLLocationCoordinate2D location; // coordinates of the annotation
NSMutableArray *newAnnotations = [NSMutableArray array]; // an array in which we'll save our annotations temporarily
MKPointAnnotation *newAnnotation; // the pointer to the annotation we're adding
// iterate through the array, adding an annotation to our our array of new annotations
for (NSDictionary *dictionary in array)
{
// retrieve latitude and longitude from the dictionary entry
location.latitude = [dictionary[#"lat"] doubleValue];
location.longitude = [dictionary[#"lon"] doubleValue];
// create the annotation
newAnnotation = [[MKPointAnnotation alloc] init];
newAnnotation.title = dictionary[#"name"];
newAnnotation.coordinate = location;
// add it to our array
//
// incidentally, generally I just add it to the mapview directly, but
// given that you have a didAddAnnotationViews, we'll just build up
// an array and add them all to the map view in one step after we're
// done iterating through the JSON results
[newAnnotations addObject:newAnnotation];
// clean up
[newAnnotation release];
}
// when done, add the annotations
[self.mapView addAnnotations:newAnnotations];