Arlo Guthrie and the origins of the Collection protocol

A bit of history to make you smile:

Rick DeNatale at Talk Like a Duck writes about
How Arlo got injected into Ruby [via Smalltalk].

During the interview he [Dan Ingalls] was asked about the origin of those enumeration methods of the Smalltalk collection classes. Alan Kay had told the interviewer that they had come from a song. At first Dan didn’t remember this but then remembered that there was a song which had a string of words like inject, select, detect etc. As far as I recall, though he didn’t name the song.

But I recognized it right away, here’s how “Alice’s Restaurant Massacree” transitions from the littering trial to the draft:

Came to talk about the draft. They got a building down New York City, it’s called Whitehall Street, where you walk in, you get injected, inspected, detected, infected, neglected and selected.

So that’s how the enumeration method names came into Smalltalk (and, later on, into Ruby)!

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Creating a Seaside “Hello World”, localhost

Table of Contents:

Note: This section assumes that you’ve mastered the basics of creating new classes and methods in Pharo Smalltalk. If not, I recommend you glance through the Paro By Example, or my own previous post on Creating Classes and Methods in Pharo.

Note 2: See also the Getting Started (Pharo and Squeak) section of Dynamic Web Development with Seaside for a similar “getting started” tutorial, with screenshots.

Time to create our first “Hello World” app in Smalltalk/Seaside. Here’s the plan:

  1. Create a new Category and component (read: class) for our app.
  2. Create a method to output ‘Hello World’
  3. Register the component with Seaside, so it can start routing requests
  4. Profit! (That is, load up the page in the browser, and behold Hello World)

1.a. Creating a Seaside Component – The How

Creating a Seaside component is easy. First, create a Category for this tutorial – something like ‘RHelloWorld-Core’. Now, inside it, create a class (a subclass of WAComponent) called, for example, RHelloWorldComponent. Like this:

WAComponent subclass: #RHelloWorldComponent
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'RHelloWorld-Core'

That’s it. You’re a third of the way done (now we just need to create a method to output ‘Hello World’, and register the component with the framework, so it can start routing).

1.b. Creating a Seaside Component – The Why

So, what is a component? A Seaside component is a subclass of WAComponent (the “WA” stands for “Web Application”, incidentally). Great, but what is it really? To answer that, we need to briefly discuss how you write web apps in Seaside.

Think of a component as a “smart view”. What about Models, though? And Controllers? Well, components that are complex enough to need models, have models. That is, Models are also a concept that Seaside uses. Since we’re just writing a static “Hello World” app, we don’t need a model, we’re just going to output a literal string directly. What about Controllers, though? Don’t we need a Controller? Well, no. Not as such. Part of the answer is – Seaside (and the programming language itself) IS the Controller. It takes on the traditional role of the controller (routing requests, calling the right objects and methods, managing sessions and marshalling parameters). Seaside also has Tasks (subclasses of WATask), which are view-less control and routing objects that manipulate other components, a job traditionally reserved for Controllers in the MVC paradigm. But again, we don’t need Tasks for a Hello World tutorial.

The easiest way to understand Seaside web development is to think of it in terms of traditional desktop GUI development. Say you open up a desktop application, like Firefox or Outlook Express. You see a window, and within it, panes and toolbars, and within those, buttons and lists and other GUI widgets. In Seaside, the application/”window” is a top-level Component, which displays sub-components (toolbars, navigation menus, panes). In a desktop app, the components keep track of their own states (and have models if need be), and have Events/Actions defined for when you interact with them (click on a button, scroll the scrollbar, and so on). Same thing in Seaside. So a Seaside app is “just” a nested collection of components, which keep track of their own states, and which register events or actions that are performed when a user clicks on a link or selects a value from a pulldown, and so on.

If that’s too confusing, or if you haven’t done desktop GUI programming, don’t worry about it. In Seaside, you’ll be dealing with Views, Models when you need them, and occasionally view-less controller-like Tasks.

2. Create a method to output ‘Hello World’

Ok, let’s create a method in our RHelloWorldComponent class. (You can either put it in the default --all-- method category, or, more correctly, create a rendering method category, and add the method there).

renderContentOn: html
	html text: 'Hello World!'.

3. Register RHelloWorldComponent with Seaside

Lastly, we need to register our component with Seaside (specifically, the Web Application Admin class), so it can start routing requests to it.

Execute the following snippet of code:

WAAdmin register: RHelloWorldComponent 
	asApplicationAt: 'helloworld'

Hold up. How do I execute code in Squeak/Pharo?
You can execute code from any code editor or workspace in the Pharo image. Traditionally, snippets of code (or “incantations”) are executed from a Workspace window, which just looks like a blank text editor window. To open one, click anywhere in the background of the Pharo window to bring the the World Menu, and select Workspace. You’ll see a blank text window. Now you can type arbitrary code in here, select it with your mouse, right-click on it and select Do It (d). The keyboard shortcut is Meta-d, of course.

Ok! Now, when you access the /helloworld url on your web server (in our case, running it by default on the desktop, it will be http://localhost:8080/helloworld), Seaside is going to locate the RHelloWorldComponent (since that’s what we registered as the top-level component of our application up above) and execute the renderContentOn: method.

Test it out – load it up in your browser, and you should see

Hello World!

displayed on a plain white html page.

Coming up next: Obtaining access to a remote server, installing Pharo on it, and packaging up your app for deployment.

A Secret: Passion and Your Choice of Web Framework

I will tell you a secret. I am passionate about Smalltalk and the Seaside web app framework. Not just on an intellectual level, “oh hey this is pretty cool, it’s got some good ideas”. But on a fire-in-my-heart level, “this is profound and important technology” kind of stuff.

Why? Good god, why? Why should a choice of language, or especially a choice of which web app framework to use, matter? Because, I believe that:

Your choice of app framework deeply affects your development speed, and your overall level of courage.

Choosing the right framework means you will finish your projects faster, and you will dare to include better and more audacious features in it.

Life is very short. You have a limited amount of time in which to realize your dreams, in which to do your projects. If you’re like me, you probably have dozens and dozens of ideas for apps, sites, portals, that you want to implement. Most of those ideas will suck. But you don’t know which ones, you won’t know until you try them. Your goal, in this life, is to iterate faster. To fail more, to fail quicker, until you get to the brilliant ideas and brilliant projects that can change the world, or at least make you a dollar or two.

I want to be able to code at the speed of thought. At the speed of dreaming. Or rather, at the speed of essential complexity, without the overhead of the accidental. See, there is a notion in computer science of Essential complexity versus Accidental complexity. Essential complexity is “Hmm, I’m trying to solve a difficult real-world problem that is complex and messy”, and accidental complexity is “why the hell can’t I easily do this simple thing in my framework?!”. And I believe that while the first will never go away, there is still too much of the second, of the overhead, of cruft, in the world of web frameworks.

Based on my experience, I believe that the Seaside framework is the most powerful and flexible one, that has the potential to come closest to “development at the speed of dreaming”. It is not quite there yet. But it can be, with not too much more effort.

Now it’s time for a confession: the fastest-to-develop in, most prototype-friendly framework that I’ve had the pleasure to work with so far is not Seaside, nor is it Ruby on Rails (which has other reasons to recommend it). It’s a relatively unknown (dare I say underdog?) Python framework called web2py, headed by Massimo Di Pierro. Its ease of use, quality of documentation and community support, and the amount (and integration) of out-of-the-box features made (on large project with a small team) development quick, easy and secure. I am seriously grateful to Massimo and the web2py community for raising my standards of what a web app framework should do.

Then what am I doing here? Why isn’t this blog called “web2py Zen”? Because, I believe that the features that make web2py fantastic (like comprehensive documentation, out-of-the-box authentication and user management, ease of use and diversity of persistence options, amazing error logging capabilities, etc) can be added to Seaside – with some effort, but it’s not impossible. Whereas the key features of Seaside (the continuations, the reuse and embedding of components, Halos and the debugging process) cannot be easily (or at all) added to web2py. Smalltalk (and Seaside) is fundamentally “upstream” to Python, in the sense that Paul Graham writes about.

So, Seaside could be my ideal web app framework. It is built on some amazing technology, and has features unsurpassed by any other framework at the moment (and has plenty of drawbacks, sure, but none unfixable). It’s going to take some work (and that’s part of what starting this blog has been about, for me), but it also has a vibrant community around it that I think is up to the task.

One more thing. While I believe that the choice of frameworks is important, and that some are, objectively, better than others (for certain goals), I don’t want the arguments over which one is better to be based solely on personal opinion. I want the frameworks to prove themselves, to pull their own weight. What I really want to see is studies, and competitions between frameworks. I want web framework olympics, of the kind that Plat-Forms is trying to do (only that’s in Germany – I would love to see more US-based ones). I want to see evidence, and experimentation. And will strive to provide some of my own.

Am I advocating that you choose one framework (that you think is best) and really focus on it, practice the hell out of it? Yes. But also: You have to try all the other frameworks. You have to periodically re-evaluate your choice. If some other framework is doing something fundamentally right, and you can easily add it to your framework, do it. If not, if they’re doing something right and profound and you can’t add it to your framework (perhaps because of language limitations), perhaps you need to reconsider your allegiance.

In any case, whatever your favorite language: Choose the right app framework. Love it, improve it, practice the hell out of it. Re-evaluate your choices periodically. And iterate faster.

Smalltalk Basic Skills – Creating New Classes and Methods

I generally assume that readers of this blog will have basic Smalltalk skills (that is, are able to at least create and edit Smalltalk code). But just in case you’re coming in from the outside, and have no experience with any kind of Smalltalk, I would like to help walk you through some of the basics.
If you find this post helpful, leave a comment, so I know to post similar walkthroughs in the future.

Main Concept – Separate Class and Method Definitions

A quick note before we start. In other programming environments, the basic unit of code is a file. Whether you’re coding in Java, PHP or Ruby, and whether you’re using Emacs, vim, TextMate or Eclipse, the process is very similar. You create a new file in your code editor window, and start typing Class and Method (function) definitions. Everything important happens in the file, in the single code window. You have other list views and panes – there’s often a section of your text editor that lists all the files you’re working on, in your project. Many IDEs and code editors also have panes that list Classes and Functions defined in a particular file. Clicking on a class or function usually jumps you to their definition in the file – these list panes are aids to navigation. But in general, package/module declarations, Class definitions and Method definitions all live in the same file.

Smalltalk (especially in modern Smalltalk environments like VisualWorks, Squeak and Pharo), separates these definitions out, each to their own little window. The Class definition gets its own window, class comments and documentation (similar to JavaDoc blocks) gets its own, and each individual method is shown separately. If this sounds confusing, or slow to work with, do not worry. The Smalltalk IDE is built for this from the ground up. In practice, once you get used to finding your way around, navigating between different classes and methods is incredibly fast, often faster than in any other coding environment.

How to Create Your First Class

Ok, let’s get to it! Open your Seaside One-click Image. That window in the middle, titled WACounter? That’s the code/system browser. If you close it by accident, you can always either press Meta-B (that’s Alt-B on windows) or click on anywhere on the background in the Pharo window and select System Browser off the World Menu.

The leftmost pane of the System Browser should be a list of categories, containing entries like Seaside-Examples-Misc. Categories are ways to group code into conceptual areas, a way to divide code into projects or applications. They are the philosophical equivalent of Packages in other programming languages.

Let’s create a Category to house our first class. Right-click on the Packages pane, and select Add category. Enter something like Tutorials-Zen in the text window that pops up, and press Enter. That category gets created and highlighted – in the bottom code pane, you will now see the following:

Object subclass: #NameOfSubclass
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Tutorials-Zen'

This is, essentially, the ‘Create a New Class’ interface. You can just start typing over the sample template text displayed there, and hit Meta-S to Save.

So, let’s create a class called MyFirstClass – highlight the word NameOfSubclass and type over it. This is what your code should look like, before you save:

Object subclass: #MyFirstClass
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Tutorials-Zen'

When you hit Meta-S, you will see the class appear in the second pane on the top.

Side Question: What happpens when I create a class without a category? Nothing much – the class gets created with a blank category. The blank category gets listed as a blank line in the Package/Category list pane, at the bottom. And now your class is harder to find. So don’t do it.

Next step: let’s create a method in our new class. So far, you’ve used two panes on the top half of the System browser. The first (leftmost) one is the Packages/Categories pane. The second one is a pane listing Classes. The third one lists method categories (also called Protocols), which is an optional way to conceptually group methods within a class. We’re going to ignore these for now, and just use the default ‘–all–‘ method category.

So, click on MyFirstClass class to highlight it. Then click on the --all-- category in the next pane (to show that you want this new method to be in the default category). The ‘new method’ code template will appear, already highlighted (making it easier for you to delete it, and start writing your own code):

messageSelectorAndArgumentNames
	"comment stating purpose of message"

	| temporary variable names |
	statements

Delete all of that sample code, and type in your own (and hit Meta-S to save). Here’s the code for a simple method that returns a string:

myFirstMethod
	"My very first method. Simply returns a literal string."

	^'Hi there!'.

Once again, after you type the code and hit Meta-S to save, the method appears in the rightmost pane of the System browser.

Question: When I hit Meta-S for the first time, a popup window prompts me for my name! What is this?
Answer: Ah, this is the system prompting you for your name or intials, so it can know who edited what code. You know how most version control systems (CVS, Subversion, Git, what have you) keep track of user names, so you can figure out who made what change to a file? This is similar. Squeak/Pharo keeps track of the revision history for each method, and it prompts you for your name the first time you change anything during a coding session.

Finally, let’s add a second method to MyFirstClass. Again, click on the ‘--all--‘ method category, highlight the sample method template, and start typing:

mySecondMethod
	"A second method of my very own"

	| aTempVariable |
	aTempVariable := 1.
	^aTempVariable.

That’s it! Now you know how to create categories, classes and methods in Smalltalk.

“Setting It Up Right” – Loading Useful Extensions into Pharo

Table of Contents:

Ok, so this section turns out to be much shorter than I expected. I mostly wanted to write about installing OmniBrowser, which is an extension/rewrite of the system-provided code editors in Squeak/Pharo. It adds all sorts of nifty icons and helpful behaviors (such as right-click on a method and be able to see its Senders and Implementors), and is a great package. And I wanted to point out that it’s kind of indispensable (at least I found it so), which is I why I would want to side-track a simple Hello World tutorial with the explanation of how to install it.

However, it turns out that OmniBrowser already comes pre-installed on the Seaside One Click Pharo image. And my adventures in trying to install it come from plain Squeak, of several years ago.

Same thing with code code coloring/syntax highlighting, and code auto-completion – installed out of the box (again, I used to have to install it manually).

With the time we saved not setting things up, it’s time to actually start learning Smalltalk syntax. For those few who are actually learning Smalltalk (or refreshing their memories after a long absense), I highly recommend diving right into the excellent free online book, Pharo By Example, and taking it from page 1.

Next up, a simple Seaside Hello World running on your desktop.

Deployed Hello World – Installing Seaside and Squeak/Pharo Basics

Table of Contents:

Time to install Seaside. If you go to Seaside Download page (and click on the Seaside for Pharo Download link), you’ll see that there are several options. The easiest one is the Seaside One-click Experience — as I mentioned in the last post, this comes with a VM for your operating system, sources, and an image that comes with Seaside installed, and a web server started and ready to go as soon as you open up Pharo. This is the option you should go with — click on the latest one (at the time of this writing, it’s Seaside One-Click Experience 3.0.3).

Where should I unzip the download file? Squeak/Pharo is self-contained, so it doesn’t matter where you install it, it’s not going to make any Windows Registry entries or anything like that. I usually place it in C:\Pharo on Windows, or in my user directory on Linux.

To Launch Seaside: (after unzipping it into a Pharo folder) click on the folder, then on Seaside.app, then on Contents, then on the folder appropriate to your operating system, then on the executable.

If the VM is in Contents\Windows\, where is the image that I’ll be launching? The image lives in Contents\Resources. The default one that launches when you double-click on the executable is Contents\Resources\Seaside.image.

Go ahead and double-click on the executable and open Pharo. (On Windows, you will likely be prompted by the OS to permit the application to open a port — that’s the web server starting up). You will see three things — a server control panel, conveniently started for you, a code browser window, and what looks like a text file but is actually a full-fledged Workspace in which you can execute code (more on those later).

Where is the menu bar? File, Edit, Windows, Help, etc? Squeak/Pharo does not have the traditional menu bar running across the top that you see on most applications on Windows, Linux or Mac. It’s kind of like Emacs in that it tries to be its own universe (although even Emacs has menu bars on most latest versions). However, what you do have is the World Menu — click on any empty spot within the Squeak window (the squeak “desktop”, if you will), that is, anywhere not on the code browser or workspace, and you will see a popup menu titled “World”. This is essentially your menu bar, and contains the items you’d expect, Help and Windows commands, preferences, and so on.

Now the vi/Emacs question – how do I save and exit? Easy enough – click on an empty space on the Squeak desktop to bring up the World Menu >, then Save or Save and quit.

Wait, if I hit World Menu > Save, and then World Menu > Quit, why does it ask me if I want to exit without saving? Didn’t I just save? Yes, you did just save, so everything’s ok. It’s just being extra paranoid. If this disturbs you, then use the ‘Save and quit’ option to do both in one step, and then it won’t prompt you with that question.

When I click on the X icon to Close Window and exit, why does the prompt say ‘Quit Croquet without saving’, instead of Quit Pharo? That’s minor bug in the current release that I’m sure is left over from merging some of the code from Croquet into Pharo, ignore it. Actually, the Croquet Project is a fascinating VR/realtime collaboration project that’s implemented in Squeak, and is worth checking out.

OK, so how do I edit code? The last basic thing you need to know is how to actually edit code from within Pharo. Click over to the code browser window (it’ll say WACounter on the title bar — that’s the name of the class it’s browsing). Now click anywhere on the code and add an extra space or a return somewhere, just to have edited it. (Btw, see how the upper right corner of the code window turns orange? That’s how you know this method has been modified). Now, to save edited code, press Alt-S (I think it’s Cmd-S on Mac). (Why does Squeak use Alt-S instead of the more traditional Ctrl-S to save a window/buffer? I’m not entirely sure, but you can change this behavior in preferences (switch how Squeak handles Alt and Ctrl keys) to be more familiar for Windows/Linux users — I’ll explain how in the next post).

When you hit Alt-S (Squeak documentation will refer to this as Meta-S (Emacs users will find this familiar), so as to be consistent across operating systems), an Information Required prompt will pop up and ask for your name. Why does it do this? Because all code edits get saved in a version log (you can see this by clicking on the Versions button above the code editing area), and entering your name allows you to identify the code edits as yours. (When you start using source control tools like Monticello, this name will be used to sign your code changes). Think of it as the @author tag in the JavaDoc tool.

Important note: Meta-S just saves the code changes to a single method within the live image, it does not save the image itself. You still have to go World Menu > Save to save the whole image to disk, before you exit (or commit your changes to a version control system, once you start using one).

How do I open another code browser window? Go to World Menu > System Browser and that opens up a code browser window (incidentally, you can switch between the open windows in Squeak by pressing Meta-Left or Meta-Right keys, kind of like switching tabs in Eclipse or Firefox).

Ok, you now know enough to be dangerous to write code. Next up, a quick note on customization, and the on to the Hello World web app in Seaside.

Deployed Hello World – Basic Smalltalk Dev Environment Concepts

Table of Contents:

Before we install Seaside, I’d like to explain some terminology.

For example, if you go to the Pharo Download Page (though that’s not the one we’ll be ultimately using for this tutorial — we’ll use the Seaside Download Page instead), you’ll see several headings – “One-Click Image”, “Custom Downloads” with subheadings of “Image”, “Source Files” and “Virtual Machines”. What are all of these? First, let’s discuss some key concepts that you will be working with in the Smalltalk world.

Key Concepts

Virtual Machine

If you’re coming from the Java world, this is the Runtime Environment. It’s a small virtual machine, specific to your operating system, that runs Smalltalk bytecode. Hence, in the “Custom Downloads > Virtual Machines” section, you’ll see binaries for Windows, OS X and Unix.

Which VM should I use, Cog VM or “standard”? Don’t worry about it for now. Use Cog, which is a new JIT VM that promises to be faster than the standard one.

Images

If the Virtual Machine is the Runtime Environment, the Images are Eclipse (or a similar IDE), your workspace (with saved preferences and windows positions) and the code you’re working on.

Let me repeat that: The Image is the IDE, your workspace AND the code that you’ll be working on.

The Image is OS-independent. (Hence why there’s only one link, say, Pharo 1.1.1. image (stable) – use this for all operating systems). That means you can develop your code on Windows, then switch over to Linux, load up the image into the VM, and continue coding exactly where you left off, down to the placement of the code editor windows on the screen.

The image is also the unit of deployment. (Again, with the Java metaphor, think of it as the .jar file, that you’ll be rolling out to the server).

Wait, if I’m deploying the image, and the image also contains the IDE and workspace, does this mean my deployed app will contain all sorts of extra cruft? Good question. No, it will not — when preparing an image for deployment, you strip away all that non-essential code. So fear not.

Why is it all integrated like that (the IDE, workspace and code)? For various historical reasons I’m still fuzzy on, and which don’t really matter in this tutorial. However, the thing to take away is this: the tight integration is not going to hurt you, it will not create bloat (see the above), and it buys you some incredibly useful development and debugging capabilities.

What about collaboration? How do multiple developers work on one image? That’s where source control comes in. Though the Squeak/Pharo world does not use the usual source control tools (CVS, SVN, Git or Mercurial), it does use source control — Monticello, a “distributed, optimistic, concurrent, versioning system”, written in Smalltalk. (Again, the theme of tight integration, of Smalltalk all the way through, down to the support and development tools). Your day to day workflow will be roughly the same working in Monticello as with other source control tools, the same concepts apply — you’ll be updating your code to the latest revision, working on it, then committing, merging with that of other developers, etc.

PharoCore images

Ignore these. These are minimalist images for advanced users and core developers of the Pharo project itself.

Source files

This is the source code to much of the Virtual Machine, as well as some libraries and core classes. (In Debian/Ubuntu world, think of this as the source packages, to go with the binaries.)
The virtual machine will still work without source files, but when you click on some of the base classes, you’ll just see bytecode, and that’s not very useful.
You’ll want source files in your environment — part of the beauty of Smalltalk is that the source for the entire stack is available for your perusal.

.changes files

Though these are not referenced on the Download page, in various Smalltalk tutorials, you’ll hear mentions of change files, as in “copy your image and .changes file to your backup directory…”. You know how some database systems keep a transaction log, so that when the db server crashes, you can still recover all of the transactions from disk? This is what the .changes file is. It’s a log of all of your actions in the workspace, so that if your image crashes or becomes corrupted, you can still recover your code and data.

How often will it crash / will I have to use the .changes file? I’ve been developing in Smalltalk for 9 years, and I haven’t had to use it yet. That doesn’t mean you won’t have to, so I just wanted to mention it.

Putting It All Together – Windows Installer, and the “one-click image”

Now that you understand the basic components of a Smalltalk dev environment, those download links help you put it all together.

The Windows installer packages together a Windows VM, a starting image, and a sources file to go with it. If you’re developing on windows, just use this.

The Pharo x.x.x one-click image is a similar packaging, except it contains VMs for all 3 OSs (Windows, Linux and OS X), as well as an image and sources to go with them. So the idea is, you just download that one distribution, and then use whichever runtime your OS requires.

Finally, the Seaside 3.0 one-click experience on the Seaside Download Page is a zip file containing all 3 OS-specific VMs, sources, and an image file with the Seaside project already loaded into it, and the web server started. This is the one we’ll be using for our Deployed Hello World.