An Introduction to WebObjects, in Swift

Days before the introduction of WebObjects 6 at WWDC 2018, let’s have a look on what WebObjects actually is. And more specifically how it could look like in Swift. A small tutorial, and an implementation of the WebObjects API in Swift, or as we like to call it: SwiftObjects.

Let’s jump back, 2 years, May 4th 2016: Apple officially killed one of Steve Job’s favorite projects:

“WebObjects is a discontinued product and will never be upgraded.”

So while WebObjects 5 (the Java version) can still be downloaded from Apple Downloads, it is discontinued by Apple for almost 10 years now (last version was 5.4.3, from 2008). Yet a surprising amount of web sites are still using it. Most prominently the dreaded iTunes Connect:

You can usually tell something is backed by WebObjects by looking at the URL:

 |          |                 |  |- custom path
 |          |                 \- WORequestHandler key (ra 🤔)
 |          \- Application Name
 \- Adapter Prefix

This literally says “WebObjects”, but the application is also named “.woa” (Web Objects Application).

Today we are going to resurrect it and have a look what made it great, and why that isn’t much relevant anymore. But before we start, we need to setup a development environment.

Project Setup

Instead of fiddling around with Swift Package Manager, we use swift xcode to use SwiftObjects directly within Xcode. Grab Homebrew if you don’t have it yet, and install the SwiftObjects image using:

brew install swiftxcode/swiftxcode/swift-xcode-wo
swift xcode link-templates

That will take a moment to install and compile, but then we are ready to go!

You’ll notice that SwiftObjects is hooked up to the excellent Swift NIO, but that doesn’t really matter here. The API can also be driven by something like mod_swift, Kitura or whatever you prefer.

Create and Run First Project

Within Xcode, create a new project (⌘-Shift-N), go to the “macOS” section and select the “WOApplication” template, very much at the bottom of the inspector (pro tip: type “wo” in the filter field at the upper right):

Give your project a name, say “HelloWOrld” create it somewhere, and you should end up with something like this:

Press the Play/Run button to build and start the application. Open your favorite browser and navigate to http://localhost:1337/:

Yay. History is up and running!

As you see we got some default content in our HTML page. That it looks a little nice is because we embed the Semantic UI CSS framework. Doesn’t really matter here, you can use anything you like.

Try something: In the form at the bottom change “Homepage” to “Hello World” and press the “Submit Query button”. The title of the page will update:

Also notice the URL in the browser, it now contains a URL generated by SwiftObjects. A so called “component action URL”. It follows the pattern we mentioned above: application name (just “Application”), request handler key (“wo” for “component action”), and extra stuff (in here, a session-id, a context-id and an element-id).

Basic Concepts

Before we continue, a small introduction on terminology and a high level overview.

WebObjects contains many cool ideas and concepts, but the key idea is to free the web application developer from having to think about low level HTTP things like “URLs”, “form parameters” or session management.

It brings Model View Controller (MVC) and Target/Action to the web.

Target / Action

Consider this controller object, called a WOComponent in WebObjects:

class Main : WOComponent {
    var counter = 0
    func incrementCounter() -> Any? {
        counter += 1
        return nil // stay on page

and this accompanying template:

  <wo:a action="incrementCounter">++</wo:a>

It may display like this:

If you press the small ++ link, WebObjects will take care of everything and call your incrementCounter method, which increments the counter, and re-renders the page.

The WOHyperlink backing <wo:a> sends the component (the target) an action (incrementCounter) when the user clicks the link. The WOHyperlink automatically generates a unique URL which represents the action and preserves the state required to resurrect the component object for a click.

Again: URL generation is automatic in WebObjects, the programmer does not have to concern himself about URLs, URL matching or anything like that! He wires up buttons to controllers using actions. Just like in UIKit!
Just like you don’t usually deal with a UIEvent in UIKit, you don’t usually have to deal with a WORequest in WO.

Model View Controller (MVC)

WebObjects generally follows the MVC paradigm.


The WOComponent is the controller, similar to a UIViewController. It interacts with the view, the model and responds to user actions. Components react to actions emitted by the controls in the view tree. For example if the user clicks a link, a WOHyperlink will call an action method in the component.

Like in UIKit, a WOComponent can embed other components, also known as controller containment. This way you can build up a complex web page from different, reusable components.


The view part is the “template”, a tree of WODynamicElement objects. Unlike the “template engines” you probably know about, a WebObjects template does not only render HTML. It also processes input, like form values or reacts to link-clicks!

For example the WOTextField not only renders the <input type="text" value="abc"> HTML tag. When a form POST request is received, it also extracts the corresponding form value and pushes the value into the controller. Like UIView’s, they do both, the “rendering” and the “event handling”.


We don’t look at the model in this blog entry. In the original WebObjects you would usually use the Enterprise Objects Framework (EOF). Today’s CoreData is essentially a reduced version of EOF. In SwiftObjects you could use ZeeQL, or any other framework you like.

Similarities with UIKit

Let’s have a look at the WebObjects classes by looking at their UIKit counterparts. If you know UIKit, you’ll feel right at home in WebObjects.

A WODynamicElement is like UIView, they “draw” the output (e.g. HTML) and they handle events. That they handle events is very different to other HTML templating frameworks. Common elements are WOHyperlink (roughly a UIButton), WOImage (like a UIImage), WOTextField (like a UITextField), or WOString (like a UILabel).

WOComponents are like UIViewControllers. Their “view” is a template, which is just a tree of WODynamicElement’s (just like UIViews form a hierarchy/tree). They are the “controller” part in the MVC design pattern, and as in UIKit, you’ll have Massive-View-Controller, if you don’t separate your concerns. For that, like UIViewControllers (controller containment), WOComponents can also be nested. Which means you can build parts of a page from different components. Note that this is again different from a simple template “include”, in that the whole tree is also used for event processing.

The counterpart to UIEvent is essentially a WORequest. If the user clicks a link in the browser, the browser will emit an HTTP request. This request is packaged in a WORequest on the WO server side. That is usually tied to a WOContext, which also carries the WOResponse, into which the WODynamicElements are going to render their visual representation.

An application is represented as a WOApplication object, usually a singleton in the server. It corresponds to the UIApplication object in iOS. There is also a WOAdaptor object, which handles the HTTP protocol (for SwiftObjects we use SwiftNIO to do that part).

Since a server doesn’t handle just one user but trillions, there is one extra class you don’t have in UIKit: WOSession, which allows you to hold per-user information. (Things which are “global” in UIKit like the current Locale, may needs to be done on a per session or context basis in WO).


  • UIViewWODynamicElement
  • UIViewControllerWOComponent
  • UIEventWORequest
  • UIApplicationWOApplication
  • ☁️ ➜ WOSession
  • UIGestureRecognizer ➜ 🤦‍♀️

The setup of our example application

Now that we know the basic classes, let go back to our example and see what the WOApplication template generated for us:

The Application group contains the global WOApplication object, the thing required to start our HTTP server, the Session and Context objects in case you want to customize them (we won’t).

Instead let’s focus on the components. The default template contains two components: Main and Frame. Main is rendered as the first page the user sees when opening the application (like the initial view controller in a storyboard). Frame is a reusable component which wraps around content of the Main component. Components are constructed from up to three files:

Controller: The Component.swift file

This contains the Swift controller class, treat it like a UIViewController. You can put properties and actions into that, which you can then bind to the view layer. Example:

import SwiftObjects

class Main : WOComponent {
    var title : String = "Hello World!"
    override func awake() { // kinda like `viewDidLoad()`
        expose(doubleTitle, as: "doubleTitle") // a Swift wart
    func doubleTitle() -> WOComponent? {
        title = title + title
        return nil // stay on this page

Note: A component is not required to have a Swift class. Like Frame in the boilerplate, you can have just a template, but still access the dynamic elements from within those! If there is no custom Swift class, SwiftObjects will use the WOComponent class.

View: The Component.html file

The Component.html file contains the template associated with the controller. Remember that in WO the template is not just for rendering. It corresponds to what you do in a XIB file. You lay out the user interface and place dynamic elements into it.

  Some text

<WEBOBJECT> tags are used to inject dynamic elements into the otherwise static HTML content. In original WebObjects you would only use those, but SwiftObjects also allows you to add elements using either: <wo:Element bindings..> or <#Element bindings ...>.

Historical sidenote: There used to be a visual design tool for WebObjects called “WebObjects Builder”. Just like in IB, you could wire up the web controls with the WOComponents. Here is a picture, and the WWDC 2000 video on how to use it.

Bindings: Component.wod

WOD stands for “WebObject Definitions”. In the template we only said we want a WebObject called “Title”, we didn’t specify what it is and how it is configured. This can be done in the .wod file:

Title: WOString {
  value          = title;
  valueWhenEmpty = "placeholder";

This says that the “Title” element is a WOString dynamic element (similar to a UILabel). What follows is a set of “bindings”. The left side is a parameter supported by the WOString, here value and valueWhenEmpty.

The right side is a so called WOAssociation, usually either a WOKeyPathAssociation or a WOValueAssociation.

The = title syntax results in a WOKeyPathAssociation. When the WOString renders its HTML to the response, it will retrieve the title property from the WOComponent, look above, this thing:

class Main : WOComponent {
    var title : String = "Hello World!" // ☜

That is, the WOString will render the text “Hello World”.

The = "placeholder" is a constant string. It is taken as-is. In this case it means that if the title is empty, the WOString will render “placeholder”.

Template Shortcuts

When typing templates without WebObjects Builder, having to type in three files quickly becomes annoying. Hence SwiftObjects supports a few shortcuts. The example above can be written without a .wod file, directly in the template:

<h1><#WOString value="$title" valueWhenEmpty="placeholder" /></h1>

Note how the $ is used to denote a keypath association.

This is another shortcut which uses a “shortname” for an element:

<h1><wo:str value="$title" valueWhenEmpty="placeholder" /></h1>

(other examples: wo:if for WOConditional, wo:for for WORepetition, wo:radio for WORadioButton, …)

Let’s build an own app: WOx

We’ll modify our application boilerplate a little. We want to use Semantic UI Cards to show a list of nice cows like that:

Step A: A store containing nice cows

First create a new Swift file called CowsStore.swift. This contains our dummy model. A basic Cow class, and a CowStore to maintain them:

final class Cow {
    // Shouldn't that be a struct?! No, we are demoing 90s tech!
    var info    : String = ""
    var image   : String = ""
    var friends : Int    = 0
    init(info: String = "", image: String = "", friends: Int = 0) {    = info
        self.image   = image
        self.friends = friends

final class CowStore {
    let urlPrefix = ""
    static let shared = CowStore()
    var cows : [ Cow ] = [
        Cow(info: "beef jerky",
            image: "carmen.jpg", friends: 0),
        Cow(info: "CompuCow Discovers Bug in Compiler",
            image: "sowmya.jpg", friends: 1337),
        Cow(info: "This cow jumped over the Moon",
            image: "gustl.jpg", friends: 42)

Step B: Render the cows as a list on the Main page

Next open the Main.swift. On this page we want to show the list of our cows. Change the title property to WOx and expose the store as a page property. Also, add a property called cow. It should look like this:

final class Main : WOComponent {
    var title = "Homepage"
    let store = CowStore.shared
    var cow   : Cow? = nil

Then open the Main.html and drop everything but the Frame top-level tag. Add this:

<!-- Main.html -->
        <WEBOBJECT NAME="CowList">
            <li><WEBOBJECT NAME="CowInfo"></WEBOBJECT></li>

Next we need to define the objects, so open the Main.wod, drop everything but the Frame and add:

// Main.wod
Frame: Frame {
    title = title;

CowList: WORepetition {
    list = store.cows;
    item = cow;

CowInfo: WOString {
    value =;

If you restart the app and connect to http://localhost:1337/, you should now see something like this:

In the “view” layer we created a WORepetition, which kinda acts like a UICollectionView: it displays a bunch of items. Let’s look at it:

CowList: WORepetition {
    list = store.cows;
    item = cow;

list and item are parameters the WORepetition supports. We bind the keypath store.cows to the list. store is the CowsStore property in our Main class. And that CowsStore has a cows property we access (an array of Cow objects).
When the page is rendered, the repetition will loop over that array and repeat its contents. While looping, the repetition will set the item binding to the current item in the list. Because we bind the item = cow, the repetition will push the current value to the cow property in our Main class.

Now looking into what is contained in the repetition, we have a:

CowInfo: WOString {
    value =;

Remember, the repetition pushed the current cow into our cow property, it contains the current cow from our cow array. Now the WOString value argument is bound to the keypath. Which grabs the info property out of the cow and renders that on screen.

Step C: A reusable Cow’mponent - CowCard.wo

Above we loop over the cows, and display a property of each using a WOString. This is awesome already, but we actually want to display nice Semantic UI Cards with all the important cow info.

To do this, we are going to create a reusable component. Select the Components group in Xcode, then invoke the new file panel (⌘-N). In that panel, select the WOComponent template:

Call the file CowCard and make sure to place it in the Components folder, you’ll end up w/ something like this:

Xcode creates a full component for you: The CowCard.swift, CowCard.html and CowCard.wod. Open the CowCard.html and drop the whole content. Insert this instead:

<!-- CowCard.html -->
<div class="card">
  <div class="image">
    <img src="<wo:str value="$cow.image" />">
  <div class="content">
    <div class="header"><wo:str value="$cow.image" /></div>
    <wo:div class="meta">
      <a>Cool Cows</a>
    <wo:div class="description"><wo:str value="$" /></wo:div>
  <div class="extra content">
      <wo:str value="$cow.friends" /> Friends

This uses the shortcut syntax we explained before. It is the boilerplate for Semantic UI Cards, with dynamic WOString items that bind to a cow key.

Edit Main.wod and change it so, that it doesn’t use a WOString anymore, but our fresh CowCard component:

// Main.wod
CowInfo: CowCard {
    cow = cow;

This cow = cow looks funky. The left side cow is the parameter of the CowCard component (the one we use in the template above). We pass over the full, current, cow (to the WOString we just passed the

Restart your app and it should look like:

This looks a bit off, but notice that in our Main component we only changed the WOString to our new CowCard, and tweaked the binding a little. It shows how easily and quickly you can switch between components, and thereby designs or different views on the same data.

It still looks a bit wrong, because in Main.html we put the cow cards into a plain HTML list <ul><li>. Open Main.html and add the necessary Semantic UI magic:

<!-- Main.html -->
  <div class="ui link cards">
    <WEBOBJECT NAME="CowList">


Aren’t those nice cow cards? You can’t but admit that they are!

We only scratched the surface, but could hopefully pass on a feeling on how using “WebObjects” feels like. The cow demo is also part of our small WOShowcase app, which comes w/ SwiftObjects. That app also demos how to create new cows and how to edit cows, w/o having to deal with form parameters or any such HTTP annoyances:

Other WebObjects Frameworks

The WebObjects framework is just one part of the larger WebObjects “product”. WebObjects also came with other increbily powerful frameworks:

  • Enterprise Objects Framework (EOF), an Object Relation Mapper (ORM). CoreData is essentially a reduced version of this. With EOF you could access arbitrary databases (say Oracle or Frontbase)
  • Direct-To-Web (D2W). This is a rule evaluation system built around KVC. You can find a small intro over here SOPE Rule System and here. This seems to be a nice video about it.
  • Direct-To-JavaClient (D2JC). Like D2W, this would automagically build Java Swing client applications. Duh.
  • Direct-To-Web-Services. You know, when “WebServices” was the big hype ;-)


Key value Coding

WebObjects relies heavily on KVC (Key/Value Coding), which is not available in (pure) Swift, nor are the necessary reflection capabilities. We provide workarounds, but such aren’t great.

Not having this removes a lot of the beauty of WebObjects from SwiftObjects. We very much hope that we are going to eventually have better reflection in Swift 5.

Web 2.0, AJAX and beyond

Most of the stuff shown is nice and useful for building Web 1 applications. That is, applications which would render their UI as HTML, on the server side, with little or no logic running in the browser.

This isn’t universally true, but todays application servers are mostly API endpoints for Web 2.0 applications running in the browser. I.e. the server is mostly hosting the model, and none of the UI anymore. While SwiftObjects has some features to support AJAX (e.g. page fragments via WOFragment), it is not how you usually build applications today.

Hence in BIG LETTERS: This is a demo and an experiment to see whether and how the WebObjects API might work in Swift. Do not try this at home, it is not how you write web servers nowadays!

If you like what you’ve seen and you are looking for a modern client framework allowing for similar component reuse, I can highly recommend Vue.js. This is a lot like WebObjects on the client side (nesting components, bindings, and all the nice stuff).


(The now kinda extinct) is definitely the largest OpenSource application based on WebObjects technology that exists. Maybe even the largest WO application ever. If you know Basecamp (the RoR application), OGo is like a Web 1.0 predecessor of that. It does contact, project, meeting management, todo lists, and even includes an IMAP4 email client.

All with an old-school Web 1.0 interface, so take care of your eyes, this is how it looked:

Yes, it is ugly by todays standards (and probably even back then). Yet consider the complex UI with many tabs, sortable table views, an outline tree view, and so on. This was only possible because the UI was composed from many different reusable components. Feel free to browse the sources of OGo, it is a big application with loads of components.

Today OGo is very much outdated. As a replacement with less functionality but much better scalability and REST behaviour, we wrote ScalableOGo which combines WebObjects ideas with a lot of the features/ideas of Zope 2. While ScalableOGo is still being deployed today (the code was hi-jacked by a Candian company), it is neither scalable nor modern anymore either 🤓


Hey, we hope you liked the article and we love feedback! Twitter, any of those: @helje5, @ar_institute.

Written on June 2, 2018