След на паутине

Originally published at Fiberglass flowers. You can comment here or there.

It hasn’t even been a ten years that DB2, one of the most, er, expensive DBMSes, got a feature needed by every other application – dataset paging.

Before, you had to use window functions rownumber() and fetch first 40 rows only. When used by Hibernate, this resulted ugliness like:

select * from (
  select inner2_.*, rownumber() over(order by order of inner2_) as rownumber_
  from (
    select  ...
    fetch first 40 rows only
    ) as inner2_
  ) as inner1_
where rownumber_ > 20
order by rownumber_

Since this summer version – DB2 9.7.2 – you can just append LIMIT and OFFSET:

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Originally published at Fiberglass flowers. You can comment here or there.

Just in case someone needs a code snippet.
This one groups Prices by PriceProvider and was intended to pick only last 5 values for each PriceProvider – but sadly, it’s impossible without window functions. Which are not supported in Hibernate in any way.

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Originally published at Fiberglass flowers. You can comment here or there.

A friend asked me for it, so probably someone might need a jumpstart in unit tests.

Here’s a short list of short (though very deep, if not best) intros.

• Except for JUnit cookbook (~2 pages) (which has a lot of “ports”, like CppUnit cookbook), I’d name:
• “Endo-Testing: Unit Testing with Mock Objects” at mockobjects.com (Tim Mackinnon, Steve Freeman, Philip Craig) (7 pages);
• “Mocks aren’t stubs” by Martin Fowler (about 7 pages);

For deeper dive, take a “xUnit patterns” book (this one is longer).

For Kent Beck’s book on TDD, shame on me - I never read it. Though after “XP explained” I don’t strive for reading his books.

// If you’re interested in XP and “XP explained” criticism, take a look at “Extreme Programming Considered Harmful for Reliable Software Development” by Gerald Keefer.

Originally published at Fiberglass flowers. You can comment here or there.

Lua recently became very popular. I encountered Lua scripting in several applications including popular games, I believe it’s used in even more then Wikipedia says.

It’s extremely simple:

• 6 data types (that’s counting “nul” and “function”),
• no C++-style OOP out-of-box (but you can program one, he-he),
• 400K of pure-C code

but is loaded with in-fashion features like

• first-class functions,
• closures,
• coroutines…
• again, Wikipedia is the best.

The only metaprogramming tutorial (with a ready code to implement virtual methods) is “Programming in Lua” book. Still, I don’t see a code to implement ad-hoc polymorphism… Maybe it’s a reason for another post

Redistributed book removed: it violated copyright.

Originally published at Fiberglass flowers. Please leave any comments there.

Update: for a ready solution (library), see official release announcement

Windows Installer on itself is a pain. WiX saves you from it, mostly wrapping the complexity into XML constructs understandable to non-gurus.

Well, not completely – you still have to know:

• why the heck shortcut didn’t appear in start menu;
• how to create a web site shortcut;
• why to create RegistryValue for a program directory you create, and that’s the simplest things. Still better then MFC…

But a very good tutorial exists, maillist is very active and it’s easy to get support.
Maybe it’s another reason to love Unix-es, where “install IS just a copy”.
Though, one has to admit that installing Windows application involves somewhat more desktop integration.

I was looking for an auto-update, so that:

• application could say “New version available, download? Restart now?“;
• would use MSI;
• download should preferably use BITS.

Simple automatic updaters like this on Codeproject won’t do, because you can’t just download necessary files: Windows Installer will revert them back. Or you would have to “disable WI’s Resiliency“, which is also a bad idea.

Solution of my choice

ClickThrough subproject of WiX promises that, but it’s still beta and crashes. Still you can easily compare two MSI files, generate a MSP patch, and a RSS feed that client can check, download and even read by eye, so simple it is – a pretty tasty feature.

There is no .NET client code. For now, there is only a separate update.exe that will find, download and install new version. Still, you cannot ask user whether to download now or not, cannot tell what’s new, when to restart, etc.
But you can painlessly add a Start menu shortcut that will update your application.

Come later, I’m going to create a C# code that will check for updates, and probably publish it.

Other solutions

You can use Updater ApplicationBlock, or more exactly, latest version now lives at CodePlex. But Enterprise Library wasn’t updated for .NET 3.5, and I believe it’s abandoned.

You can use NSIS. Though, it’s not Windows Installer MSI packager, it creates own files and scripts.

For ClickOnce application, you can use Application.Deployment.