A day in the life of...

I always say this so I have probably blogged it in the past, in light of my MOZY incident probably recently, but "It's not how good you are when things go right, it's how good you are when things go wrong". My wife and I are (unexpectedly) expecting our 4th baby.  We paid for a private scan at MUMS last week.  Part of the package is a DVD of the scan.  The scan was a really good one, but unfortunately when we got home we realised our DVD was completely blank. I phone them up and they offered a free scan.  I was still disappointed because there was a beautiful part of our previous scan that would be lost, where we were zoomed right into our baby's hand as she repeatedly clenched and reopened her hand, but I agreed because at least we would have something . When we had our scan they gave us probably double the normal amount of time.  In addition to that they upgraded our scan from a plain ultra sound to one of those 4D scans.  We were given twice as many printed ph

If you are unaware Bletchley Park played a vital part in World War II, it undoubtedly shortened the war (possibly by years) by decoding intercepted Nazi messages which had been encoded on the Enigma machine.  This site is credited with being the place where the first programmable computer was used to crack the more complex Lorenz Cipher Machine. According to this petition number 10 Downing Street... http://petitions.number10.gov.uk/BletchleyPark/ ...the park is severly lacking in funds and has at best 2 to 3 years before it is forced to close down.  The idea that a site with such a historical significance could be bulldozed and redeveloped is astonishing! Please help to preserve this computer related historical UK site by making as many UK residents as possible aware of this petition!

Jonas has just added the following feature to ECO 5 which should turn up in the next build. Let's say you have a package with a single class LockObject in it. This LockObject must have TimeStamp locking, but you use this package in many applications.  In ECO 5 you can set the default locking mode for a package. Now let's say you have multiple packages that you use in many applications and the locking type is different per app.  App 1 uses AllMembers locking, App 2 uses no locking at all; how can you specify the locking type?  Now you can add a .NET attribute to the top of your application specific EcoSpace class.... [UmlTaggedValue("Eco.OptimisticLocking", "AllMembers")] public class Application1EcoSpace : DefaultEcoSpace {   etc.... } Locking is determined like so: The kind specified on the class itself. The kind specified on any super class. The kind specified on the package. The kind specified on the EcoSpace.

Someone I know recently got stung by this, so I thought I’d mention it... static void Main(string[] args) {   int a = 1;   int b = a;   Console.WriteLine(AreSame(a, b).ToString());   Console.ReadLine(); } static bool AreSame(object a, object b) {   return a == b; } What’s the output to the console? Does a equal b? Even if you didn’t know the answer you will have guessed it is False otherwise this blog would be totally pointless! It’s false because the parameter types of AreSame are both "object". For a value type such as "int" to be passed as an object it needs to be boxed, so a new object instance is created which stores the value "1", but this is done for both parameters so we end up with 2 new instances both holding the value 1. 1 equals 1 for value types but the default comparison for System.Object is to compare references. If they are not the exact same object (and in this case they are not) then the result is false. Now if we typecast both a and

A company I have been contracting for decided to use AccuRev as its source control solution. I've not liked it from the start because it is too much work, the terminology in it is quite frankly stupid, and it is far too "chatty" when you work remotely.  Anyway, for some time now I have suspected it has been losing source code. On a few occasions I have found myself looking at source code and thinking "I could swear I have already done this!". Well, last week I wrote some pretty nice code which used multiple threads in a test case to ensure I experienced expected behavior when multiple users update the same objects in a database.  Today one of the other programmers said to me "Didn't you write more tests than this?" and showed me the tests.  My multi-threaded tests were gone! I knew it all along, but now it is indesputible, AccuRev has been losing my work!

My copy of this book has just turned up. I am book hungry these days, can't wait to read it :-)

I’ve just finished reading What every programmer should know about object oriented design . The first couple of sections are a bit useless really, but the 3rd section is very good. I particularly liked the section on the difference types of connascence in software. There’s some basic information about it here if you fancy a brief overview of what it is about. It’s a really good book, I recommend you read it! Should only take a day if you only read the 3rd section.

http://java.sun.com/blueprints/corej2eepatterns/index.html It was only $0.41 used in the USA, came to about £6 with posting to the UK. I don't write Java and at the moment have no interest in learning it, but I expect I will be able to read it without problems (never really looked at it). So why did I buy this book? Because it is about this... That's why :-)

Just found out that I can do this too public invariants   Overdraft >= 0 : ’OverdraftGreaterThanOrEqualToZero’;   Balance + Overdraft >= 0 : ’BalancePlusOverDraftGreaterThanOrEqualToZero’; end; Then in my handler routine I get that message! if not IsValid then   throw new Exception(ErrorMessage); Excellent :-)

I’ve been looking at Prism some more recently. I’m a bit annoyed with myself really because someone has been telling me to look at it for years but I wanted to concentrate on C#. Now that I am looking at it I see things in there which I really like. Recently I am looking at invariants, pre-conditions, and post-conditions. First let me show you the invariant support. An invariant is like a class constraint, it specifies a condition which must be true but when must it be true? type   BankAccount = public class   public     property Balance : Decimal read write;   public invariants     Balance >= 0;   end; The invariant is enforced each time a public method exits. Actually it is enforced after the post-conditions of a public method exits but we don’t have any post conditions yet. class method ConsoleApp.Main; begin   var account : BankAccount := new BankAccount();   //The next line throws an assertion error   account.Balance := -1; end; Property getters and setters are considered

In my previous post I showed an interface ILockable. The actual interface is public interface ILockable {   Guid GetLockID();   Type GetLockObjectType(); } Any lockable resource implements this interface. In its constructor it creates an instance of a class which descends from LockObject, a Document class for example would create an instance of DocumentLockObject which descends from LockObject. The "Document" class would store away the ID of the DocumentLockObject in a private attribute. Now when my LockingService is asked to lock multiple (un-related) instances which implement ILockable I want to do this 1: Create a new EcoSpace 2: Load objects efficiently 3: Get locks 4: Update the DB 5: Dispose of the EcoSpace If I experience an OptimisticLockingException then loop and try again. The item I would like to discuss is #2, "Load objects efficiently". In my model a LockObject has a *--1 association to Session identifying which session has locked it, I want to en

This might seem like a bit of an odd requirement. I am currently implementing an offline pessimistic locking service in an ECO app. This will mean that I can use a LockingService to place read/write locks on objects. As usual I have gone for an interface approach (ILockable) rather than making all my lockable classes descend from a base Lockable class. Remember, it's what I DO , not what I AM . The idea is that I have a Lockable object which holds a list of Sessions. These Sessions indicate who has a read lock, and who has a write lock on the object. Each ILockable business entity will create its own private instance of Lockable when it is created. The thing is, this application will at times need to lock thousands of objects in as little time as possible. As there is no common ancester for these ILockable classes I can't just use EnsureRelatedObjects to traverse an association name and load all LockObject instances in a single select. I decided that what I needed was to

Drop a DefaultORMappingBuilder component next to your persistence mapper. Point PersistenceMapperxxxxx1.NewMappingProvider and RuntimeMappingProvider to point to this new component. On your PersistenceMapper component expand SqlDatabaseConfig and click the [...] next to KeyMappers, ensure that you have an item named "GuidMapper" with the MapperTypeName set to "Eco.Persistence.GuidKeyMapper". If not then add it. On your DefaultORMapperBuilder set IdKeySignature to System.Guid (case sensitive). Set its IdMapperName to GuidMapper. Now regenerate your DB.

I’ve played a little more with Prism. I find it a little difficult to mentally code on two levels. Level one being the code I am writing for the aspect, and level two being the code I am writing which will executed by the target. Having said that, as soon as I ran my app and saw the output everything was worthwhile. Here is my Person class type   [aspect: EcoAspects.BusinessClass(’DomainClasses.Package1’)]   Person = public class   private     FFirstName: String;     FLastName: String;   protected   public     property FirstName : String read FFirstName write FFirstName;     property LastName : String read FLastName write FLastName;   end; here is the code which uses that class class method ConsoleApp.Main; var   P: Person; begin   P := new Person();   for A in typeOf(Package1).GetCustomAttributes(true) do     Console.WriteLine(a.ToString());      P.FirstName := ’Peter’;   P.LastName := ’Morris’;   ShowGetValueByIndexResult(P as ILoopBack2, 0);   ShowGetValueByIndexResult(P as ILoop

Sometimes you have a list of objects (say List<PurchaseOrder>) and you want to get all associated objects (say OrderLines) for all the orders in the list. There are 2 ways of doing this in ECO You call a PersistenceService method which takes the list of orders and a string identifying the association name. I don't like this approach because the name of the association may change during modelling and this wont be picked up as an error until runtime. You use the overloaded method which takes an IAssociationEnd. I don't like this either because you have to find the IAssociationEnd instance from the meta-model at runtime, and to do this you'd probably use a name anyway. So, what's the alternative? public static void EnsureRelatedObjects<T>(this IPersistenceService instance, IEnumerable<T> objects, Expression<Func<T, object>> member) where T : IEcoObject {     MemberExpression memberExpression = (MemberExpression)member.Body;     instance.Ensure

I am playing with Prism’s new Aspect Oriented Programming feature. As a learning exercise I am implementing some of the features ECO requires on a class. If all goes well I will end up with aspects I can apply to plain classes and have them run in ECO. One of those features is the ILoopBack2 interface. In order to tackle this interface a small piece at a time I have created my own ILoopBack2 interface, so far with only one method. ILoopBack2 = public interface   function GetValueByIndex(I: Integer): System.Object; end; This method allows the ECO to evaluate OCL (Object Constraint Language) expressions such as "self.FirstName" and have them route via the class’s property, just in case there is any logic in the getter. By implementing an interface which uses an index to identify the property to read it is possible to avoid reflection. So, getting on with it, here is my class definition type   [aspect: EcoAspects.BusinessClass(’DomainClasses.Package1’)]   Person = public cla

This is fun :-) I’ve created an aspect like so type   BusinessClassAttribute = public class(System.Attribute, ITypeInterfaceDecorator)   private     FPackageName: String;     property PackageName: String read FPackageName;   protected   public     constructor (PackageName: String);     method HandleInterface(Services: RemObjects.Oxygene.Cirrus.IServices; aType: RemObjects.Oxygene.Cirrus.ITypeDefinition);   end; I can now decorator my class like so type   [aspect: BusinessClass(’DomainClasses.Package1’)]   Person = class   end; I can ensure this class  exists in the aspect implementation method. constructor BusinessClassAttribute(PackageName: String); begin   FPackageName := PackageName; end; method BusinessClassAttribute.HandleInterface(Services: RemObjects.Oxygene.Cirrus.IServices; aType: RemObjects.Oxygene.Cirrus.ITypeDefinition); var   PackageType: ITypeReference; begin   PackageType := Services.FindType(PackageName);   if (PackageType = nil) then     Services.EmitError(’Package cl

Here’s what I did. 01: I created a support project which just has a logger class in it. namespace EcoSupport.pas; interface uses   System.Collections.Generic,   System.Linq,   System.Text; type   Logger = public class   private   protected   public     class procedure Log(Message : String);   end; implementation class procedure Logger.Log(Message : String); begin   System.Diagnostics.Debug.WriteLine(’Log: ’ + Message); end; end. 02: I created an Aspect which decorates methods, giving me the opportunity to intercept all method calls on the class it decorates. namespace EcoAspects; interface uses   System.Collections.Generic,   System.Linq,   System.Text,   RemObjects.Oxygene.Cirrus,   EcoSupport; type   [AttributeUsage(AttributeTargets.Class)]   LogAspect = public class(System.Attribute, RemObjects.Oxygene.Cirrus.IMethodImplementationDecorator)   private   protected   public     method HandleImplementation(Services: IServices; aMethod: IMethodDefinition);   end; implementation method