From JavaScript to Objective-C with JSON

Question

I have no idea how to properly 'return' this JSON object (in JavaScript):

function callback() {   
                var points = '{\"points\": [';
                var params = polyline.getLatLngs();

                var i;
                for (i = 0; i < points.length; i++) {
                    params = params.concat('{\"latitude\": ', points[i].lat, ', \"longitude\": ', points[i].lng, '}');
                    if (i < points.length - 1) {
                        params = params.concat(', ');
                    }
                }
                params = params.concat('] }');

                return JSON.parse(params);
            }

I want to catch it with something like (Objective-C):

NSString *s = [self.webView stringByEvaluatingJavaScriptFromString:@"callback();"];

Obviously this results in a NSString, what I really want is NSData to do this (Objective-C):

NSData *data = [s dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *response = [NSJSONSerialization JSONObjectWithData:data options:NSJSONWritingPrettyPrinted error:&error];

So, how to properly return the JSON?

I'm sorry, did you just construct a JavaScript object in JavaScript by concatenation, then parse it? — Ry-
– Ry- ♦, Commented Mar 20, 2012 at 22:51
What @minitech means is that JavaScript natively understands JSON syntax - you don't have to construct a string like that and parse it; you can just create the object directly. — Pointy
– Pointy, Commented Mar 20, 2012 at 22:56

user123444555621 · Accepted Answer · 2012-03-20 23:08:39Z

1

This should do it:

function callback() {
    var params = polyline.getLatLngs();
    var result = [];
    var i;
    for (i = 0; i < params.length; i++) {
        result.push({latitute: params[i].lat, longitude: params[i].long});
    }

    return JSON.stringify({points: result});
}

Note that JSON.parse generates an object from a string, and JSON.stringify creates a string from an object. No need to do it manually.

answered Mar 20, 2012 at 23:08

user123444555621

154k27 gold badges118 silver badges126 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

From JavaScript to Objective-C with JSON

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related