Skip to main content

Roslyn shopping cart DSL – Part 3

Image
By

An effective way to create a DSL is by building a thin layer that runs on top of a façade that interacts with the domain objects.
This is how those components looks in the sample app of this post.
In this case, the DSL only talk to the façade and the façade is in charge of talking with domains objects (or services or whatever component that goes underneath). This makes things really easy to implement and fit perfectly to work with Roslyn, because if we use the façade as the Roslyn script engine’s host object, the engine will let us access directly from our DSL syntax to any member of the façade's public API.

By looking at this unit test you will see how to wire up the components, execute the DSL script and modify the order state (the domain object) right from the DSL.


* If this were a real app, the order will continue with the processing pipeline.

So far so good, now how to go from our DSL syntax to façade calls?
* Notice that the facade exposes the domain object's state and/or behaviour..

If you take a look at the façade public API you will notice that almost every member matches with conditions and actions available on our DSL syntax (switching from Pascal Case to snake_case). As we mention earlier, any public member of the host object (in this case the façade) will be available right out of the box to our DSL, so with a little bit of source to source translation, this is pretty easy to achieve.

How to configure the façade as the engine’s host object
Configure the host object is pretty straight forward, it only takes a few lines of code.

And the rest of the work relies pretty much on source to source translation, which I will be covering in futures post.


Labels:

Comments

Post a Comment

Popular posts from this blog

Migrating an ASP.NET MVC 4 app from Azure websites to WinHost

By
About a week ago I've to migrate an ASP.NET MVC 4/EF5 application from Azure websites to WinHost. While the process was really smooth, there were some caveats related to database connections that I want to share with you. Create and setup the ftp profile on VS and configure the connection string was really easy, WinHost provide you those values and there is nothing special here. But once you deploy your website and try to see it online, you may get the “yellow screen of dead” with the message: "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)" Assuming you wrote the connection string properly, this happens because you cannot use the default connection name in your web.c
2 comments
Read more

How to show excel files inside the .NET Webbrowser Control

By
If you are reading this, chances are you been banging your head against the wall for a couple of hours (or even days) trying to show excel files inside the WinForms webbrowser control. Possible reasons you ended up in here: You had working code that got broke after upgrading from Win 7. Your code doesn’t work the same way between machines running different (newer) versions of IE. A download box pops up every time your app tries to show an excel file inside the webbrowser control (you wanna show the actual content). You just have no clue on how to get excel working into the .NET embedded webbrowser control. You are trying to implement IInternetSecurityManager and don’t know where to start. (Or how don’t know how to delegate calls to your security manager). Among many other, maybe….. Yes, COM is a PITA, so is ActiveX and IE (Embedded or full for that matter). And no, showing excel files inside the webbrowser control shouldn’t be that hard, but sometimes we have
3 comments
Read more

Moving to Medium

By
It's been a long time since I want to give medium a try, and finally, I made some time to do it. To get started on the new platform, I'll be doing series on "Getting programming concepts, languages and tools". If it sounds interesting to you, please take a look at the first post  Getting AWK  and spread the word if you like it. I'm not going to migrate old entries to the new web site. They will remain here safe and sound! As usual, thanks for reading!
Post a Comment
Read more