An Alternative to CodeSmith
I'm a big fan of code-generation for automating boiler-plate code. I used to use CodeSmith for this, but the freeware version is no longer maintained. T4 is my new favourite tool for code generation, and there's a wealth of information available on using it on Oleg Sych's site.
Passing Command-Line Parameters to TextTransform
The tools come with a command-line host for T4 (TextTransform.exe), but there's no obvious way to pass parameters to the templates.
You can pass parameters using the command-line option -a:
TextTransform.exe
-a mappingFile!c:\myPath\MyClass.hbm.xml
-out c:\myGeneratedFiles\MyClass_Generated.cs
c:\myTemplates\GenerateNHibernateProperties.tt
In order to retrieve the parameter from inside the template, you can use a little reflection:
private string GetCommandLineProperty(string propertyName)
{
PropertyInfo parametersProperty =
Host
.GetType()
.GetProperty("Parameters",
BindingFlags.NonPublic | BindingFlags.Instance);
StringCollection parameters =
(StringCollection)parametersProperty
.GetValue(Host, null);
foreach (string parameter in parameters)
{
string[] values = parameter.Split('!');
int length = values.Length;
if (values[length - 2] == propertyName)
return values[length - 1];
}
return null;
}
Replacing NHibernate Magic Strings
Now I can loop through my .hbm.xml files in my build, generating the 'magic strings' for the properties of each class (example template and project is linked below).
This turns code like:
IList<Media> mediaWithNameAndType =
DomainRegistry.Repository
.CreateQuery<Media>()
.Add(Expression.Eq("OwningLibrary", this))
.Add(Expression.Eq("Type", media.Type))
.Add(Expression.Eq("Name", media.Name))
.List<Media>();
Into code like:
IList<Media> mediaWithNameAndType =
DomainRegistry.Repository
.CreateQuery<Media>()
.Add(Expression.Eq(Media.Properties.OwningLibrary, this))
.Add(Expression.Eq(Media.Properties.Type, media.Type))
.Add(Expression.Eq(Media.Properties.Name, media.Name))
.List<Media>();
Some links:
- Example template to retrieve TextTransform.exe parameters
- Example template to generate NHibernate magic strings
- Example project that generates NHibernate Magic Strings in the build
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