iOS JSON数组和MapKit

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];