SBJson (aka json-framework)

SBJson (aka json-framework)

JSON (JavaScript Object Notation) is a light-weight data interchange format that's easy to read and write for humans and computers alike. This library implements strict JSON parsing and generation in Objective-C.
Notable changes in 3.1
Automatic Reference Counting (ARC) Support

Version 3.1 requires Xcode 4.2 to build, because previous versions did not have ARC support. If you can't use Xcode 4.2, or for some reason can't use ARC, you need to stick with SBJson version 3.0.
New Features, Changes, and Notable Enhancements in 3.0
JSON Stream Support

We now support parsing of documents split into several NSData chunks, like those returned by NSURLConnection. This means you can start parsing a JSON document before it is fully downloaded. Depending how you configure the delegates you can chose to have the entire document delivered to your process when it's finished parsing, or delivered bit-by-bit as records on a particular level finishes downloading. For more details see SBJsonStreamParser and SBJsonStreamParserAdapter in the API docs.

There is also support for writing to JSON streams. This means you can write huge JSON documents to disk, or an HTTP destination, without having to hold the entire structure in memory. You can use this to generate a stream of tick data for a stock trading simulation, for example. For more information see SBJsonStreamWriter in the API docs.
Parse and write UTF8-encoded NSData

The internals of SBJsonParser and SBJsonWriter have been rewritten to be NSData based. It is no longer necessary to convert data returned by NSURLConnection into an NSString before feeding it to the parser. The old NSString-oriented API methods still exists, but now converts their inputs to NSData objects and delegates to the new methods.
Project renamed to SBJson

The project was renamed to avoid clashing with Apple's private JSON.framework. (And to make it easier to Google for.)

    If you copy the classes into your project then all you need to update is to change the header inclusion from #import "JSON.h" to #import "SBJson.h".
    If you link to the library rather than copy the classes you have to change the library you link to. On the Mac JSON.framework became SBJson.framework. On iOS libjson.a became libsbjson-ios.a. In both cases you now have to #import <SBJson/SBJson.h> in your code.

API documentation integrated with Xcode

The InstallDocumentation.sh script allows you to generate API documentation from the source and install it into Xcode, so it's always at your fingertips. (This script requires Doxygen to be installed.) After running the script from the top-level directory, open Xcode's documentation window and search for SBJson. (You might have to close and re-open Xcode for the changes to take effect.)
TweetStream Example Project

An example project showing how to use the new streaming functionality to interact with Twitter's multi-document streams. This also shows how to link to the iOS static lib rather than having to copy the classes into your project.
DisplayPretty Example Project

A small Mac example project showing how to link to an external JSON framework rather than copying the sources into your project. This is a fully functional (though simplistic) application that takes JSON input from a text field and presents it nicely formatted into another text field.
Features also present in previous versions

    BSD license.
    Super-simple high-level API: Calling -JSONValue on any NSString instance parses the JSON text in that string, and calling -JSONRepresentation on any NSArray or NSDictionary returns an NSString with the JSON representation of the object.
    The SBJsonParser and SBJsonWriter classes provides an object-oriented API providing a good balance between simplicity and flexibility.
    Configurable recursion depth limit for added security.
    Supports (but does not require) garbage collection.
    Sorted dictionary keys in JSON output.
    Pretty-printing of JSON output.

Installation

The simplest way to start using JSON in your application is to copy all the source files (the contents of the Classes folder) into your own Xcode project.

    In the Finder, navigate to the $PATH_TO_SBJSON/Classes folder and select all the files.
    Drag-and-drop them into your Xcode project.
    Tick the Copy items into destination group's folder option.
    Use #import "SBJson.h" in your source files.

That should be it. Now create that Twitter client!
Upgrading

If you're upgrading from a previous version, make sure you're deleting the old SBJson classes first, moving all the files to Trash.
Linking rather than copying

Copying the SBJson classes into your project isn't the only way to use this framework. With Xcode 4's workspaces it has become much simpler to link to dependant projects. The examples in the distribution link to the iOS library and Mac framework, respectively. Des Hartman wrote a blog post with step-by-step instructions for iOS.
Links

    GitHub project page
    Example Projects
    Online API docs
    Frequently Asked Questions