Posts

ECO IV

CodeGear are letting some people blog about features in the next release of Delphi (Highlander) before it has even been released. How cool is that? A lot less secrecy, what a great move! Sooooo. How about I spill some beans about ECO IV? Maybe I can find a thing or two to mention :-) I'll just throw together something unplanned, so expect a weird mixture of stuff in no logical order whatsoever! Well, first of all , you're going to get a whole load of source code. I mean *lots* of it! There's a new service called the ICacheContentService . Let's say you know for a fact that there is an object in the DB with the ECO_ID 1234 and it is a Customer. Instead of loading that object into the cache with an OclPS evaluation you can simply use this service to register it in the cache. I've found this really useful in an app I am writing where I use SQL to find customers matching a certain sales criteria. I then create an IObjectList of these customers by injecting the

More secure passwords

Storing a plain-text password in a DB leaves your system open to abuse from anybody with access to the tables (sys admin for example). Here is the technique I recently used. Instead of storing the password itself I store a hash of the password, and a random "salt" that was used to create the hash to make it less predictable. [UmlTaggedValue("Eco.Length", "255")] private string PasswordHash { get { ... } set { ... } } [UmlTaggedValue("Eco.AllowNULL", "True")] [UmlTaggedValue("Eco.Length", "40")] private string PasswordSalt { get { ... } set { ... } } As you can see I do not store the password, just a hash + salt, both of which are private. Here are the methods used to set the values of these properties. public void SetPassword(string newPassword) { if (newPassword == null) throw new ArgumentNullException("password"); if (newPassword.Length < 6) throw new

Printing bitmaps using CPCL

I've had no end of grief trying to print a PCX to a Zebra Printer using the CPCL printer language. Silly me, didn't notice the EG command (expanded graphics) so there was no need to convert my BMP to a PCX and then struggle with binary data. I still had a bit of grief working out how to print using the EG command because the documentation is quite frankly crap. The expected command format is EG {WidthInBytes} {HeightInPixels} {XPos} {YPos} {Data}\r\n The printer expects a 1 bit pixel matrix. So if pixel(0, 0) is set you will set "80" in the data. If pixel(0, 0) is set and pixel (7, 0) is also set you would sent "81". Basically what you need to do is to read each set of 8 horizontal pixels and then use bit operations to create a byte value 0..255, and then output this as hex 00..FF. Here's the routine :-) public void DrawBitmap(Bitmap bmp, int xPosition, int yPosition) { if (bmp == null) throw new ArgumentNullException("bmp");

The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

This new compile error was driving me mad! My project used to work, then I upgraded to a newer version of ECO. There were 3 projects using an EcoSpace, 2 would compile but not the 3rd. In the end the solution was simple but annoying to track down so I thought I'd mention it here just in case anyone ever strolls across it and finds it useful. In my licenses.licx files for the 2 projects I had the line Eco.Handles.DefaultEcoSpace, Eco.Handles but in the project that was failing somehow a strong name had been used, even though I originally entered it manually! Changing it back to the weak name fixed the problem.

Source control

At work we use SourceSafe for our version control, and I used SourceAnyWhere as the client. I would like to outline the facts and let you decide what happened for yourself. 01: I checked out my model (EcoModeler) 02: I added a new class. 03: Generated code. 04: Checked in the mode. 05: Checked out. 06: Added two new associations 07: Generated code. 08: Checked in. 09: Checked out. 10: Added a parameter to a method. 11: Changes a state machine diagram. 12: Checked in. After each of the changes I would implement code in my application that used them, so if the changes were lost at any point during this process then I would notice because my app would no longer compile. Today I checked out the model and noticed that my new class was missing. I backed up my generated source code and then regenerated code from the model. Using BeyondCompare I checked for differences and came up with the list of changes in the steps above. Somehow the model in my source control had 3 revisions missing. I

UndoBlocks, SyncServer, and multiple EcoSpaces

In an ECO app I am writing it is very important that updates by other users are identified as soon as possible. This is because there will be multiple users all selecting jobs to do from a predefined list, and it is not only possible but also very likely that more than one user will select the same job at the same time (the job at the top of the list). To implement this I chose to use the remote persistence feature of ECO and in particular its Sync Server feature. Every 5 seconds my client apps will contact the server and retrieve a list of updates made by other users, it will then apply those updates to the cache of its own EcoSpace. So when a user selects a job to do at the top of the list their app will stamp it as InProgress and update the DB, the job will then automatically disappear from the screens of all other users. As I like to use undo blocks in my app to allow the user to cancel changes (using my DirtyObjectCatcher component) it is highly likely that during these synchro

CapableObjects announced

There are exciting times ahead! The team that brought you ECO for Delphi are now a separate company named Capable Objects ( http://www.capableobjects.com ). ECO will still be part of the next release of Delphi, but according to the official statement ( http://dn.codegear.com/article/3673> ) and comments in the newsgroups it is quite obvious there will also be a version of ECO for Visual Studio! In the past the ECO guys released patches for ECO bugs, unfortunately it was not always possible to provide a patch. With the guys now being a separate company they are free to decide their own release schedules. Instead of having to wait for a Delphi update they can now release updates as often as they wish. Just like the good old BoldSoft days when we used to get an official update really quickly if ever a critical bug was found. Not only that, but it would also seem that they will be shipping source code too! But that's not all John! The guys at Capable Objects have asked me to wr