Just announced rather silently in the Symbian Developer Newsletter, one of the biggest changes in the world of Symbian OS development is on its way. It's all about the letter L, which represents the new idiom of L-classes. According to the documentation PDF: "The L prefix denotes that these classes may be Liberal when it comes to Leaving, while being Leave-safe themselves."

When working with Symbian OS and of course especially when teaching it, the biggest issue have always been the descriptors. While they are a nice concept and a good example of polymorphism, even the simplest string modifications often required looking up some code examples or documentation. Now, the new LString class can finally take care of automatically resizing its buffer (on the heap) and memory cleanup. Additionally, the LString is also derived from TDesC, making it possible to use it with all the standard Symbian OS APIs.

Other changes include the possibiliy to put everything from the two-phase construction into a single C++ constructor, by using macros and special templates. Makes the code easier to read and shorter, and is therefore also a welcome change. Memory management (plus cleanup stack) usage has also been simplified through the use of new class templates (LCleanedupX and LManagedX), which provide automatic resource management.

We'll see how these new additions work out in real life, but at least on paper, they do sound promising and make it easier for newcomers to start developing with Symbian OS. The only problem is that those new concepts are added to many other already existing idioms, increasing the total amount of information you have to know when you really want to do a lot - and it'll not be possible to get entirely rid of old descriptor classes like the HBufC, as they're still used by many system APIs. Also, that these resource management tasks are done automatically usually means less efficiency compared to the manual way that has always been in Symbian OS - one of the reasons why the OS is so fast, even on low spec hardware. Most probably, you'd use native Symbian OS C++ code for the more low-level and highest performance code (and do resource management manually), and prefer Qt or Widgets instead for other applications in the future.

Another interesting sidenote: if you take a look at the new header files, you'll see that they are already released under the "Symbian Foundation License v1.0" (even though the source code is not included yet) and that they are contributed by Nokia. In case I didn't miss anything, this is most probably the first public third party contribution to the Symbian Foundation. Let's hope we'll see more of those welcome additions in the future - even though it means that I'll have to rewrite many parts of the Symbian OS course slides when there's time...

Read more about the L-classes at the Symbian Developer Network, especially at the pdf linked to at the end of the article.