The JSON Validator

Just plunk your JSON string into the window and press the validate button. Voila, not only are you told if your JSON string is valid but it also arranges your JSON data in an easily readable hierarchy. The JSON Validator was made and shared by the good folks at lab.ac9.com.Thank you arc90!



If you like what you come up with you can use the ‘Get & Share’ button in the top right corner of the widget to email, link, embed or spread your creation.

Also by Hobnox is Audiotool, a music production environment in your browser. Super fun. Be warned, you may loose hours of your life if you follow the links.

JSON logo

The JSON format is often used as an alternative to XML to transmit structured data over a network, its biggest use being in Ajax web application programming.

Below are instructions for how to retrieve and parse JSON formatted data in an iPhone app.

Adding JSON Framework To Your XCode Project

To use JSON in an iPhone app you first need to download the JSON Framework for Objective-C from its Google Code page.

When it is downloaded, mount the DMG.

Finally, drag and drop the JSON directory onto the Classes folder icon in the Groups & Files panel in XCode.

Retrieving JSON Data

First of all make sure that you include the JSON.h file in your implementaion(your .m file):

#import "JSON.h"

To retrieve JSON data use an NSURLConnection to issue an HTTP request. To do this you will need an NSMutableData variable to hold the response data. Create it in the interface (.h file) with:

NSMutableData *responseData;

and

@property (nonatomic, retain) NSMutableData *responseData;

and don’t forget to synthesize in the implementation (.m file):

@synthesize responseData;

Next you need to make an HTTP request with NSURLConnection so start by initializing responseData:

responseData = [[NSMutableData data] retain];

Then make the request:

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.someurl.com/somefile.json"]];
[[NSURLConnection alloc] initWithRequest:request delegate:self];

Then you need to include the following methods to process the NSURLConnection and save the JSON data into the responseData variable:

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
	[responseData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
	[responseData appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
	label.text = [NSString stringWithFormat:@"Connection failed: %@", [error description]];
}

Making Use Of The JSON Data

To make use of the JSON data use the connectionDidFinishLoading: method. Here is an example with some simple error checking:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
	[connection release];

	NSString *responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
	[responseData release];

	if ([responseString isEqualToString:@"\"Unable to find specified resource.\""]) {
		NSLog(@"Unable to find specified resource.\n");
	} else {
		NSDictionary *dictionary = [responseString JSONValue];
		self.someVariable = [dictionary valueForKey:@"somekey"];
	}
}

In this connectionDidFinishLoading: method you can use any of the key names you know to be in the JSON data to get their values and store them or use them as you need.

Hopefully this helps you to get started using JSON data in your iPhone apps.

I am happy to announce that my Pachube feed organizer/viewer application PachubeMon is now available as a free download on the App Store. It was also announced on the Pachube blog on Monday.

PachubeMon iPhone app

Pachube is a web service available at pachube.com that enables you to connect, tag and share real time sensor data from objects, devices, buildings and environments around the world.

PachubeMon is a utility app for the iPhone that lets you manage and view your Pachube feeds all in one place. The main page allows you to add and remove feeds. By selecting a feed from the list you can view it. You can find feed IDs on the Pachube website here.

For a fascinating deeper look at Pachube and the concepts around it, check out the amazing article and interview here.

I have already sent off a request for an invitation to the beta version and am watching my inbox with excitement. I can’t wait to use an arduino to start logging some data to share online. I would love to track the sun light in my garden or the energy usage in my house or use Pachube as part of a home automation system. Perhaps I will be able to monitor how much time I spend making music versus downsurfing on the interweb!

There is already a convenient way to follow peoples Pachube feeds on your iPhone but it might also be interesting to explore the API and create a handy Pachube iPhone app of my own.