In his excellent book, Beginning Scala, David Pollak provides a series of statements that can be considered as a recipe for avoiding the use of null values in your Scala code. I've organized his statements here in the following three sections.

1) General rules about null and Option

We begin with the following general rules regarding the use of null values in Scala code:

Way back in late 1998 (think "before Google"), I started devdaily.com in the hope that it would one day grow into a website where authors would offer tips and tutorials for Java, Perl, C, C++, Linux, and any other open source programming language and technology that came along. Then in 1999 I started a company named Mission Data, and I put the dream of devdaily aside.

Summary: A discussion of the Option/Some/None pattern in Scala, and how to use Either/Left/Right instead of Option/Some/None when you need to know why something failed.

A Scala idom is to use the Option/Some/None pattern instead of using exceptions and try/catch/finally (especially using Option/Some/None instead of using null values), but a weakness of this approach is that the Option/Some/None approach doesn't tell you why something failed, that is, why you got a None instead of a Some.

I can never remember the name "unfiltered", so yesterday I kept trying to google for "web service framework", and to my surprise, Google wasn't showing unfiltered. In fact, it didn't show other tools like Scalatra, though it did show Play in the top ten.

So today's post is an effort to help Google out a little bit here. If you're looking for good Scala web service frameworks, check out these tools:

Scala SBT FAQ: How do I put SBT into "offline mode" so I can use it while working on an airplane, or any other location where I don't have a WiFi connection?

Use this setting at the SBT command prompt:

> set offline := true

Warning: I honestly don't know how well this works. I have tried it a few times, and I know it prints out a ton of output, but I haven't paid attention to all that output to see exactly what it does.

To reverse the setting, just change it to false instead of true:

I ran across the following page in the book Clean Code, and it really caught my attention. In short, there is a programming language named LOGO that apparently used to keyword TO in the same way languages like Scala and Ruby use "def". This is described near the bottom of the page in the following image, in the area I highlighted:

I'm sorry, I don't know the original source of this image about "delegation" in computer programming (starring Inigo Montoya of The Princess Bride), but it's pretty funny, so I thought I'd post it here:

If you ever need to write some Scala (or Java) code where you add a JSON string to the body of an HTTP POST request, here's a quick example of how to do it using the Apache HttpClient library methods:

I just started using tmux last week, and created a cheat sheet to help me remember the basic tmux commands, and I thought I'd share that here.

The cheat sheet has a few things that are specific to my configuration file, so to begin with, here is my ~/.tmux.conf file: