# IronRuby, Silverlight and executing code dynamically in the browser

**URL:** <https://www.ruby-forum.com/t/ironruby-silverlight-and-executing-code-dynamically-in-the-browser/192030>\
**Category:** IronRuby\
**Created:** [July 22, 2010, 3:40pm UTC](https://www.ruby-forum.com/t/ironruby-silverlight-and-executing-code-dynamically-in-the-browser/192030 "2010-07-22T15:40:14Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Jonas\_FollesSSSS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/d78d45/32.png) [@Jonas\_FollesSSSS](https://www.ruby-forum.com/u/Jonas_FollesSSSS)\
**Post date:** [July 22, 2010, 3:40pm UTC](https://www.ruby-forum.com/t/ironruby-silverlight-and-executing-code-dynamically-in-the-browser/192030/1 "2010-07-22T15:40:14Z")

</div>

I’m toying around with the idea of a simple in-browser “coding  
environment”  
for IronRuby, think JSFiddle but for DLR languages. I’m fairly new to  
IronRuby, but have lots of Silverlight experience. I have gotten the  
basics  
up and running, but have ran into a couple issues.

My initial idea was to use the virtual file system the IronPython  
Silverlight Host creates when it downloads files included using   
tags. However, turns out this virtual file system is read-only, so I  
cannot  
write new Ruby files after the application is loaded.

My second idea was to simply use the DynamicEngine and simply execute  
the  
code. The code I’ve written looks something like this:

```
        def run_tests
            code = window.eval("codeEditor.getCode()").to_s
            test = window.eval("testEditor.getCode()").to_s

            puts code

            begin
                dyneng = DynamicEngine.new
                engine = dyneng.runtime.get_engine("ruby")
                scope = dyneng.create_scope

                errorFormatter = ErrorFormatter::Sink.new

                resultCode =

```

engine.create\_script\_source\_from\_string(code).compile(errorFormatter).execute(scope)  
resultTest =  
engine.create\_script\_source\_from\_string(test).compile(errorFormatter).execute(scope)

```
                puts resultCode
                puts resultTest
            rescue => ex
                puts ex.to_s
            end
        end

```

It basically gets two pieces of Ruby code, then creates a new engine,  
creates script source, compiles it, and then executes it. If I do this  
with  
valid Ruby code everything works as expected. However, if I try to  
execute  
invalid code I was expecting my error handler to execute. But this does  
not  
happen. All I get is an error in the FireBug console saying:

“Error calling method on NPObject!”

So does anyone have suggestions on how to handle errors when executing  
the  
code dynamically in the browser. Secondly, does anyone have suggestions  
for  
alternative approaches to implementing this - i.e. make the virtual file  
system writable (write to isolated storage perhaps?).

Best regards,  
Jonas Follesø

---

<div class="post-metadata">

**Author:** ![Jonas\_FollesSSSS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/d78d45/32.png) [@Jonas\_FollesSSSS](https://www.ruby-forum.com/u/Jonas_FollesSSSS)\
**Post date:** [July 23, 2010, 12:27am UTC](https://www.ruby-forum.com/t/ironruby-silverlight-and-executing-code-dynamically-in-the-browser/192030/2 "2010-07-23T00:27:49Z")

</div>

Hey Jonas, nice running into here (love your blog)!

You could try writing your own virtual filesystem. Check out my blog  
for  
some inspiration:  
[http://charlesstrahan.com/blog/2010/05/05/enumerating-resources-in-silverlight/](http://charlesstrahan.com/blog/2010/05/05/enumerating-resources-in-silverlight/)

I’m currently working on just that. My current project (porting RPG  
Maker  
XP to Silverlight - already finished the desktop port) requires such  
functionality for enumerating file system entries (think Dir.glob), and  
saving game state to “disk”. I’m trying to tease out my VFS into  
something  
extensible; you can find my code here:  
[http://github.com/cstrahan/silverlightvfs](http://github.com/cstrahan/silverlightvfs)

There’s not much there, but perhaps the PathUtil could be handy:  
[http://github.com/cstrahan/silverlightvfs/blob/master/src/SilverlightVFS/PathUtil.cs](http://github.com/cstrahan/silverlightvfs/blob/master/src/SilverlightVFS/PathUtil.cs)

The more I work on abstracting out the core of the VFS, the more I feel  
like  
it’s hard to make a “one-fits-all” sort of solution; the use cases can  
vary  
a lot. I almost think it would be better to publish some guidance and a  
reference implementation, rather than try to create some architecture  
that  
is either too abstract or, conversely, not extensible enough to be  
useful…

Let me know where you go with your project - it sounds cool.

Cheers,  
-Charles

---

<div class="post-metadata">

**Author:** ![Jonas\_FollesSSSS](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/d78d45/32.png) [@Jonas\_FollesSSSS](https://www.ruby-forum.com/u/Jonas_FollesSSSS)\
**Post date:** [July 23, 2010, 11:13am UTC](https://www.ruby-forum.com/t/ironruby-silverlight-and-executing-code-dynamically-in-the-browser/192030/3 "2010-07-23T11:13:23Z")

</div>

Hi Charles,

And thanks for the comment about my blog - really appreciate it!

I had a look at your blog post for a custom virtual file system - and I  
do  
think that is the best long-term approach. This would enable a nice “in  
browser” coding experience where you can add files, reference other  
files  
etc. all client side running in the browser.

If you look at the code in the  
[http://github.com/ironruby/ironruby/blob/master/Hosts/Silverlight/Microsoft.Scripting.Silverlight/BrowserVirtualFilesystem.csfile](http://github.com/ironruby/ironruby/blob/master/Hosts/Silverlight/Microsoft.Scripting.Silverlight/BrowserVirtualFilesystem.csfile),  
there is a class called IsolatedStorageVirtualFilesystem that extends  
the BrowserVirtualFileSystem. The class overrides the GetFileInternal  
method, throwing an not implemented exception, and have a TODO comment.  
So I  
guess this would be a good starting point.

Alternatively you could extend the HttpVirtualFilesystem, which is the  
file  
system used by the standard Browser PAL. The HttpVirtualFileSystem will  
use  
the XapVirtualFileSystem to check if a file exists in the XAP, if not it  
will try to download it. My suggestion would be to add an extra check -  
if  
it doesn’t exist on the server, then check Isolated Storage.

You would probably also have to extend BrowserScriptHost class and  
BrowserPAL, which currently expose the BrowserVirtualFileSystem, and  
instead  
use the IsolatedStorageVirtualFileSystem, as well as changing the  
OpenInputFileStream method, which throws an exception if any other file  
mode  
than Open or Read is passed in. This is the exception that bites you if  
you  
dry to use Ruby file APIs to write a file in a standard DLR app today.

It would be nice if someone who worked on the Silverlight hosting  
environment for IronRuby could chip in with suggestions on how to best  
implement write support in the virtual file system. I would be more than  
happy trying to implement this and submit a patch.

As for your blog post on enumerating resources that looks handy - as  
file  
enumeration is also something that would be useful (when the app loads  
it  
would be nice to check which files have been stored in isolated storage,  
and  
that way enabling devs to save their work in isolated storage between  
sessions).

I had a look at your SilverlightVFS code - but I guess the thing I don’t  
quite get is the proper way to “blog” a new file system into the  
Silverlight  
PAL.

- Jonas

On Fri, Jul 23, 2010 at 12:16 AM, Charles S. \<