The Node.js ⇆ Objective-C bridge


The Node.jsObjective-C bridge

NodObjC exposes the Objective-C runtime to Node.js in a high-level, easy to use fashion. It uses the BridgeSupport files to dynamically generate an API from an Objective-C "Framework", and uses node-ffi to dynamically interact with the Objective-C runtime.

Essentially, NodObjC is similar in nature to the other popular Objective-C scripting bridges:

So you can write entire Cocoa or iOS GUI applications entirely in Node.js JavaScript! Applications are interpreted at runtime through the V8 engine, rather than compiled to a machine exectuable. This has the advantage of being able to tweak code without having to recompile; excellent for rapid prototyping and development, or for those GUI applications where absolute speed is not a requirement (i.e. most). So what are you waiting for? Get to coding!

Install using npm, of course!

$ npm install NodObjC

Or add it to the "dependencies" section of your package.json file.

var $ = require('NodObjC')
// First you import the "Foundation" framework 
// Setup the recommended NSAutoreleasePool instance 
var pool = $.NSAutoreleasePool('alloc')('init')
// NSStrings and JavaScript Strings are distinct objects, you must create an 
// NSString from a JS String when an Objective-C class method requires one. 
var string = $.NSString('stringWithUTF8String', 'Hello Objective-C World!')
// Print out the contents (toString() ends up calling [string description]) 
//   → Prints "Hello Objective-C World!" 

Be sure to check out the full API docs.

This module offers a bi-directional bridge between Node.js and the Objective-C runtime. What does that mean exactly? Well due to the design of the Objective-C runtime, it is possible to port the entire API to other languages. There are quite a few bridges for Obj-C so one for node was a necessity.

So with this module, you get access to all of the Objective-C APIs, but you invoke them through JavaScript. Obj-C has a concept of "message passing" to invoke methods on objects. The way that you pass messages around is probably a little bit different than the kind of JavaScript you're used to:

// In JavaScript, you invoke a function on an object like: 

Compared to:

// In NodObjC, you send a message to an object like: 
obj('func', arg)

In Objective-C, the names of methods are part of the arguments that you pass along:

[array insertObject: obj
       atIndex: 5]

The equivalent of the above message invocation in NodObjC syntax would be:

array('insertObject', obj,
      'atIndex', 5)

So the even numbered arguments are the parts of the method name that will be invoked, and the odd numbered arguments are the Obj-C arguments themselves. In the above example, the insertObject:atIndex: function will be invoked.

In NodObjC, not only is the Objective-C runtime exposed, but so are the corresponding C functions that usually go along with these APIs (thanks to BridgeSupport). So for example, we can make an NSRect by calling the NSMakeRect() C function:

$.NSMakeRect(5, 10, 8, 30)
// -> NSRect struct 

There's a plethora of other Objective-C resources and tutorials out there.

You should definitely have Apple's official Mac or iOS API docs handy at all times.

If you're looking for support for developing with/for NodObjC you might want to join the mailing list, and check out the #nodobjc channel in the Freenode IRC server.

Additional topics of discussion can be found on the Wiki page.