Thorn (Thor for .NET)

A command line utility accelerator.

In 30 secs

For building a "Tasks" style command line utility.

1. In VS2010, Create a new "Console Application" project.
2. Install "thorn" from nuget
3. Make your code look like this:

Program.cs:

class Program
{
	static void Main(string[] args)
	{
		Thorn.Runner.Run(args);
	}
}

Protocol.cs:

[ThornExport]
public class Protocol
{
	[Description("Says 'Hello'")]
	public void Hello(HelloOptions opts)
	{
		Console.WriteLine("Hello, {0}!", opts.Target);
	}
}

public class HelloOptions
{
	[Description("Object of the salutation")]
	public string Target { get; set; }
}

Run it at the commandline:

C:\...\bin\Debug>MyApp protocol:hello -t world

Get Usage Info:

C:\...\bin\Debug>MyApp help
C:\...\bin\Debug>MyApp help protocol:hello

In 2 Minutes

Thorn essentially provides a lightweight routing and dispatch layer to you own code. Such an environment encourages a style of development which relies on application-aware utilities, and also serves as a good springboard for experimentation, and ensures that one-offs that work out are already built in a repeatable, deployable, reusable fashion. In short, your admins will love you.

To facilitate zero-friction "exports to the commandline", Thorn makes a few assumptions.

First it discovers types and methods to be exported via a reflection scan. The default convention scans the entry assembly for types marked with the [ThornExport] attribute and exports the public methods of those types. Methods marked with the [ThornIgnore] attribute will be skipped.

When an exported method is invoked, it's parameter type is examined and bound from the commandline switches by cbrianball's excellent Args library. Thorn also leans on Args to generate the help text about available switches to a command.

Therefore there are a couple of simple requirements on exported types and methods:

• Exported types must be public and instantiable (non-abstract, non-static)
• In the default configuration, exported types must have a default constructor
• Exported methods must be instance methods
• Exported methods must be parameterless or have exactly 1 parameter
• Parameter may be complex. See Args docs for details

Overriding the defaults

You have the opportunity to bend and break a number of these rules. To set advanced configuration options, use an initializer as below:

var runner = Thorn.Runner.Configure(config => {
	config.DoNotScan();
	config.Export(typeof(MyUndecoratedType));

	config.UseTypeScanningConvention(new MyTypeScanningConvention());
});

runner.Run(args);

Dependency Injection

I often wish to have services injected into my exports. Luckily it's pretty easy. To wit:

var runner = Thorn.Runner.Configure(config => {
	config.UseCallbackToInstantiateExports(ObjectFactory.GetInstance);
});

A word on namespaces

Thorn uses the names of types as namespaces, and the names of methods as actions. By default, a namespace will be required to call an action or get help for it. You can configure a "default type" as below, and then call actions on that type without a namespace.

So, modifying the 30 second example to

Thorn.Runner.Configure(config => config.SetDefaultType<Protocol>()).Run(args);

would allow commandline syntax like

C:\...\bin\Debug>MyApp hello -t world

and

C:\...\bin\Debug>MyApp help hello

It is never wrong to use the namespace for a command

Changelog

####1.0.1:

• Moved home to littlebits on github. Updated project links.
• Deprecating DoNotScan() in lieu of a more precise DoNotScanEntryAssembly()

MIT License

Copyright (c) 2011 Jace Bennett and contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.