Personally, I’d use C# as the scripting language. The .NET framework (and Mono, thanks Matthew Scharley) actually includes the compilers for each of the .NET languages in the framework itself.
Basically, there’s 2 parts to the implementation of this system.
-
Allow the user to compile the code
This is relatively easy, and can be done in only a few lines of code (though you might want to add an error dialog, which would probably be a couple dozen more lines of code, depending on how usable you want it to be). -
Create and use classes contained within the compiled assembly
This is a little more difficult than the previous step (requires a tiny bit of reflection). Basically, you should just treat the compiled assembly as a “plug-in” for the program. There are quite a few tutorials on various ways you can create a plug-in system in C# (Google is your friend).
I’ve implemented a “quick” application to demonstrate how you can implement this system (includes 2 working scripts!). This is the complete code for the application, just create a new one and paste the code in the “program.cs” file.
At this point I must apologize for the large chunk of code I’m about to paste (I didn’t intend for it to be so large, but got a little carried away with my commenting)
using System;
using System.Windows.Forms;
using System.Reflection;
using System.CodeDom.Compiler;
namespace ScriptingInterface
{
public interface IScriptType1
{
string RunScript(int value);
}
}
namespace ScriptingExample
{
static class Program
{
///
/// The main entry point for the application.
///
[STAThread]
static void Main()
{
// Lets compile some code (I'm lazy, so I'll just hardcode it all, i'm sure you can work out how to read from a file/text box instead
Assembly compiledScript = CompileCode(
"namespace SimpleScripts" +
"{" +
" public class MyScriptMul5 : ScriptingInterface.IScriptType1" +
" {" +
" public string RunScript(int value)" +
" {" +
" return this.ToString() + \" just ran! Result: \" + (value*5).ToString();" +
" }" +
" }" +
" public class MyScriptNegate : ScriptingInterface.IScriptType1" +
" {" +
" public string RunScript(int value)" +
" {" +
" return this.ToString() + \" just ran! Result: \" + (-value).ToString();" +
" }" +
" }" +
"}");
if (compiledScript != null)
{
RunScript(compiledScript);
}
}
static Assembly CompileCode(string code)
{
// Create a code provider
// This class implements the 'CodeDomProvider' class as its base. All of the current .Net languages (at least Microsoft ones)
// come with thier own implemtation, thus you can allow the user to use the language of thier choice (though i recommend that
// you don't allow the use of c++, which is too volatile for scripting use - memory leaks anyone?)
Microsoft.CSharp.CSharpCodeProvider csProvider = new Microsoft.CSharp.CSharpCodeProvider();
// Setup our options
CompilerParameters options = new CompilerParameters();
options.GenerateExecutable = false; // we want a Dll (or "Class Library" as its called in .Net)
options.GenerateInMemory = true; // Saves us from deleting the Dll when we are done with it, though you could set this to false and save start-up time by next time by not having to re-compile
// And set any others you want, there a quite a few, take some time to look through them all and decide which fit your application best!
// Add any references you want the users to be able to access, be warned that giving them access to some classes can allow
// harmful code to be written and executed. I recommend that you write your own Class library that is the only reference it allows
// thus they can only do the things you want them to.
// (though things like "System.Xml.dll" can be useful, just need to provide a way users can read a file to pass in to it)
// Just to avoid bloatin this example to much, we will just add THIS program to its references, that way we don't need another
// project to store the interfaces that both this class and the other uses. Just remember, this will expose ALL public classes to
// the "script"
options.ReferencedAssemblies.Add(Assembly.GetExecutingAssembly().Location);
// Compile our code
CompilerResults result;
result = csProvider.CompileAssemblyFromSource(options, code);
if (result.Errors.HasErrors)
{
// TODO: report back to the user that the script has errored
return null;
}
if (result.Errors.HasWarnings)
{
// TODO: tell the user about the warnings, might want to prompt them if they want to continue
// runnning the "script"
}
return result.CompiledAssembly;
}
static void RunScript(Assembly script)
{
// Now that we have a compiled script, lets run them
foreach (Type type in script.GetExportedTypes())
{
foreach (Type iface in type.GetInterfaces())
{
if (iface == typeof(ScriptingInterface.IScriptType1))
{
// yay, we found a script interface, lets create it and run it!
// Get the constructor for the current type
// you can also specify what creation parameter types you want to pass to it,
// so you could possibly pass in data it might need, or a class that it can use to query the host application
ConstructorInfo constructor = type.GetConstructor(System.Type.EmptyTypes);
if (constructor != null && constructor.IsPublic)
{
// lets be friendly and only do things legitimitely by only using valid constructors
// we specified that we wanted a constructor that doesn't take parameters, so don't pass parameters
ScriptingInterface.IScriptType1 scriptObject = constructor.Invoke(null) as ScriptingInterface.IScriptType1;
if (scriptObject != null)
{
//Lets run our script and display its results
MessageBox.Show(scriptObject.RunScript(50));
}
else
{
// hmmm, for some reason it didn't create the object
// this shouldn't happen, as we have been doing checks all along, but we should
// inform the user something bad has happened, and possibly request them to send
// you the script so you can debug this problem
}
}
else
{
// and even more friendly and explain that there was no valid constructor
// found and thats why this script object wasn't run
}
}
}
}
}
}
}