Fix it Pat

Friday, 2 November 2007

Today at Blackwood Train station, I was interviewed by a Sunday Mail journalist.

Apparently they are running a campaign to encourage more investment in public transport, particularly after the problems the trains had yesterday with the computer system failing completely.

I didn’t make the copy in the final article - oh well.

Owen Vinall, 56, of Coromandel Valley and Susan Lewis, 49, of Blackwood ride the Belair train this morning. Picture: JENNIE GROOM

Looks like I will need to get Owen’s autograph after all (he’s the guy on the left). I was sitting just out of shot behind the guy standing up near the door on the right :-)

Building Rhino Tools from the trunk

Sunday, 28 October 2007

I read about the release of Binsor 2.0, and thought that might be really handy for a current project. The problem is that you need to compile it yourself.

This was causing me a few headaches and one late night after a countless false starts I gave up and posted to the Rhino Tools Dev group.

Prerequisites

You will need the command-line SVN tools (even if you already have TortoiseSVN).

Directory layout

I’ve used the following directory layout (with SVN repository paths):

I then saved RhinoTools-Trunk\BuildFromTrunk-Config.build.sample to BuildFromTrunk-Config.build and edited it like this:

<?xml version=“1.0” encoding=“utf-8”?>

<Project DefaultTargets=“Update-All;Build-All;Copy-To-Artifact-Dir” xmlns=“http://schemas.microsoft.com/developer/msbuild/2003”>

<PropertyGroup>

<Configuration>debug</Configuration>

<Enable-Tests>false</Enable-Tests>

<Dest-Dir></Dest-Dir>

<Dest-Lib-Dir>$(Dest-Dir)\lib\$(Configuration)</Dest-Lib-Dir>

<Dest-Tool-Dir>$(Dest-Dir)\tools</Dest-Tool-Dir>

<Tools-Dir>$(MSBuildProjectDirectory)\SharedLibs\Tools</Tools-Dir>

<NH-Dir>$(MSBuildProjectDirectory)\..\NHibernate-Trunk\nhibernate</NH-Dir>

<Castle-Dir>$(MSBuildProjectDirectory)\..\Castle-Trunk</Castle-Dir>

<Rhino-Dir>$(MSBuildProjectDirectory)</Rhino-Dir>

<Artifact-Dir>$(MSBuildProjectDirectory)\Trunk-Artifacts</Artifact-Dir>

<MSBuildCommunityTasksPath>$(Tools-Dir)</MSBuildCommunityTasksPath>

<Svn-Dir>$(Tools-Dir)\Subversion</Svn-Dir>

</PropertyGroup>

</Project>

The final thing that caused me grief was some missing edits to RhinoTools-Trunk\rhino-commons\Rhino.Commons\Rhino.Commons.csproj. Hopefully this will be patched soon, but I had to make the following hand-edits to the csproj file:

Index: Rhino.Commons.csproj =================================================================== — Rhino.Commons.csproj (revision 908) +++ Rhino.Commons.csproj (working copy) @@ -158,7 +158,9 @@ - + + +

I then opened a Visual Studio 2005 Command Prompt (“Run as Administrator” on Vista), and entered:

msbuild BuildFromTrunk.build /t:Build-All

3 minutes and 44 odd seconds later, Rhino.Commons.dll appeared.

One thing to note, this is built of the trunks of NHibernate and Castle Project code, so those bits may or may not be as stable as the most recent public releases.

G3 on the way

Friday, 19 October 2007

It is with great excitement that I can now announce that we’re expecting our third child, due in May next year.

Not specifically “one for the country”, but at least with our extension almost finished we should have enough room for everyone!

Strongly-typed primary key identifiers

Friday, 19 October 2007

Often the primary keys for tables are integer types. One problem can occur when you accidentally use the OrderID when you really meant to use CustomerID. This bug can happen inside the database and it can also arise in your code data layer.

One solution for this at the code level is to create custom types (eg. OrderIdentifier and CustomerIdentifier) so that the compiler will throw an error if you try and assign or compare different types.

The down-side to this is that because Integers are value types, you can’t just inherit from the Integer class. Instead you need to store the actual integer value inside the class and expose it through a property.

eg.

Public Class OrderIdentifier

Private _value As Integer

Public Property Value() As Integer

Get

Return _value

End Get

Set(ByVal Value As Integer)

_value = Value

End Set

End Property

Public Sub New()

End Sub

Public Sub New(ByVal value As Integer)

Me.Value = value

End Sub

End Class

I’ve also noticed that NHibernate doesn’t like having custom types for primary keys, as it tries to use the System.Type.IsAssignableFrom method to see if it can convert an Integer to the OrderIdentifier object (which fails).

I’m not sure that there’s a workaround for that, as I think it would require a class to inherit from the Int32 structure, which isn’t possible.

ActiveWriter for NHibernate

Wednesday, 17 October 2007

Like NHibernateAddin, ActiveWriter is an add-in for Visual Studio 2005.

It leverages the DSL functionality to allow you to model classes and relationships and it generates the NHibernate mapping and class files (in VB or C#).

I think this has the potential to meet all my requirements for doing the hard work of class and mapping generation.

Gökhan (the main developer) has done a great job, though his focus is more on C#, so I’ve submitted some bugs (and worked on some patches) to improve the VB side of things.

One thing that is missing at the moment, is that if you drop tables onto the design surface one at a time, they don’t automatically add relations with existing classes. I did discover yesterday that if you drop multiple tables at the same time, it does figure out the relations and add them in.

One of my patches adds support to clean up the class property names. If your database naming strategy means that your column names have some kind of common prefix, you probably don’t want that in the property name.

For example, given the following database table:

CREATE TABLE [dbo].[TEST_CONTENT]

(

[TC_ID] [int] IDENTITY(1,1) NOT NULL,

[TC_TEST] [int] NOT NULL,

[TC_CONTENT] [int] NOT NULL

)

If you set the model’s “Property Name Filter Expression” property to the regular expression ^\w+?_ it will then remove the text up to the first underscore for each property name, so that you end up with a class like this:

TestContent Class Diagram

Future improvements