Right now I’m porting DBConan to C++, specifically using the QT framework (version 4.5.3). I’ve never programmed in C++ before, so the problem I’m posting here actually is an (embarrassing) basic problem in C++: it doesn’t compile :), with error message “file f_primaryKey has incomplete type”. The source code of the domain model is available here (yes, as a devout OO programmer I always start with the domain model) :D.
For those who are experienced in C++, please help me identify what exactly is the problem. I did all I knew: I’ve forward-declared the class PrimaryKey (see the top of DomainModel.h). No luck.
UPDATE: Found why. Here is the fixed code (separate file, those interested -- including myself, for not getting into the same issue -- can compare it with the earlier version). In a few words, it's another wrinkle I just learned in C++: when you declare "PrimaryKey primaryKey;" as an instance variable of "Table", I guess the compiler will look for the empty-args constructor of PrimaryKey, somewhere in the code, before the declaration of class Table. Of course, in this case, the forward declaration of PrimaryKey doesn't help as it only declares the type, not the constructors. So, the solution: use pointer. So, instead of "PrimaryKey primaryKey;", try "PrimaryKey* p_primaryKey;". Another possible way out (I think): partial class..., but there's no such thing in C++ :). Keywords for google: +"field has incomplete type" C++Ok, why C++? Well, I’ve never programmed in C++, though I always wanted too. The original DBConan – the prototype – was writen in Python because I had to run it on a UNIX machine, on which I didn’t have permission to install Java…, python was my only choice. It turned out to be a good thing for me, I could appreciate python more.
Hope that helps (I also googled using that phrase, but I didn't really find a direct / specific answer). I figured out what I explained above by doing some quick experiments.
Then, as I already stated in the presentation, this DBConan will have to have a GUI. For usability, analytic functions (which would be really difficult to use without GUI), eye-candies, etc. I decided not to use Java (swing) simply because… I’ve done Java for too many years. I need some change :). I’ve heard that QT is one of the better GUI framework out there, and it’s in C++. I read the book on programming QT (3 years ago), I liked it, and finally now I have a good excuse to use it :).
One of my first concerns was: memory management. As I wrote in my earlier post, in my understanding, in (standard) C++ we have to worry about who is responsible for deleting objects created (e.g.: the calling functions? or the one got passed in the object?). I know there’s auto_ptr in standard C++, but since I’m in QT why don’t we use what QT provides (and work well with the rest of QT framework). So I skipped auto_ptr entirely and go straight to QSharedData and QSharedDataPointer. In my case I decided to use QExplicitlySharedDataPointer, since I think it’s the model that resembles most closely the model in Java / C# that I’m familiar with.
Ok, I’m thinking here, guys, especially uni students: if you are interested in building something useful, using QT, for your thesis maybe, why not consider working with me on this?Well, I found DBConan quite useful. In my previous project in Nextel Mexico, the vendor required us to include relevant snapshot of the database whenever we report an issue / finding. Initially I did it the “normal way” (during learning phase): I did the querying manually, hoping from one table to another, and stop when I think I’ve covered the required subset. I quickly realized it was a waste of my time, so I wrote DBConan that allowed me to “slurp” the data quickly. I think this can be used in other situations that involve working with large and complex database structure.
Please email me if you’re interested. Favor de escribirme si te interesa. Silahkan menyurati saya (email) jika anda tertarik. raka.angga@gmail.com. It has to be in QT 4.5.x.
