Meta-Abstraction -- You Ain't Gonna Need It!
Posted by bsstahl on 2020-05-18 and Filed Under: development
When we look at the abstractions in our applications, we should see a description of the capabilities of our applications, not the capabilities of the abstraction
Let’s start this discussion by looking at an example of a simple repository.
public interface IMeetingReadRepository
IEnumerable<Meeting> GetMeetings(DateTime start, DateTime end);
It is easy to see the capability being described by this abstraction – any implementation of this interface will have the ability to load a collection of Meeting objects that occur within a given timeframe. There are still some unknown details of the implementation, but the capabilities are described reasonably well.
Now let’s look at a different implementation of the Repository pattern.
public interface IReadRepository<T>
IEnumerable<T> Get(Func<T, bool> predicate);
We can still see that something is going to be loaded using this abstraction, we just don’t know what, and we don’t know what criteria will be used.
This 2nd implementation is a more flexible interface. That is, we can use this interface to describe many different repositories that do many different things. All we have described in this interface is that we have the ability to create something that will load an entity. In other words, we have described our abstraction but said very little about the capabilities of the application itself. In this case, we have to look at a specific implementation to see what it loads, but we still have no idea what criteria can be used to load it.
public class MeetingReadRepository : IReadRepository<Meeting>
IEnumerable<Meeting> Get(Func<Meeting, bool> predicate);
We could extend this class with a method that specifically loads meetings by start and end date, but then that method is not on the abstraction so it cannot be used without leaking the details of the implementation to the application. The only way to implement this pattern in a way that uses the generic interface, but still fully describes the capabilities of the application is to use both methods described above. That is, we implement the specific repository, using the generic repository – layering abstraction on top of abstraction, as shown below.
public interface IMeetingReadRepository : IReadRepository<Meeting>
IEnumerable<Meeting> GetMeetings(DateTime start, DateTime end);
public class MeetingReadRepository : IMeetingReadRepository
IEnumerable<Meeting> GetMeetings(DateTime start, DateTime end)
=> Get(m => m.Start >= start && m.Start < end)
// TODO: Implement
IEnumerable<Meeting> Get(Func<Meeting, bool> predicate)
=> throw new NotImplementedException();
Is this worth the added complexity? It seems to me that as application developers we should be concerned about describing and building our applications in the simplest, most maintainable and extensible way possible. To do so, we need seams in our applications in the form of abstractions. However, we generally do not need to build frameworks on which we build those abstractions. Framework creation is an entirely other topic with an entirely different set of concerns.
I think it is easy to see how quickly things can get overly-complex when we start building abstractions on top of our own abstractions in our applications. Using Microsoft or 3rd party frameworks is fine when appropriate, but there is generally no need to build your own frameworks, especially within your applications. In the vast majority of cases, YAGNI.
Did I miss something here? Do you have a situation where you feel it is worth it to build a framework, or even part of a framework, within your applications. Please let me know about it on Twitter @bsstahl.
Intro to WebAssembly Using Blazor
Posted by bsstahl on 2018-09-26 and Filed Under: event
I will be speaking tonight, 9/26/2018 at the Northwest Valley .NET User Group and tomorrow, 9/27/2018 at the Southeast Valley .NET User Group. I will be speaking on the subject of WebAssembly. The talk will go into what WebAssembly programs look and act like, and how they run, then explore how we as .NET developers can write WebAssembly programs with Microsoft’s experimental platform, Blazor.
Want to run your .NET Standard code directly in the browser on the client-side without the need for transpilers or browser plug-ins? Well, now you can with WebAssembly and Blazor.
WebAssembly (WASM) is the W3C specification that will be used to provide the next generation of development tools for the web and beyond. Blazor is Microsoft's experiment that allows ASP.Net developers to create web pages that do much of the scripting work in C# using WASM.
Come join us as we explore the basics of WebAssembly and how WASM can be used to run existing C# code client side in the browser. You will walk away with an understanding of what WebAssembly and Blazor can do for you and how to immediately get started running your own .NET code in the browser.
The slide deck for these presentations can be found here IntroToWasmAndBlazor-201809.pdf.
Office Lens–Magic in a Free App
Posted by bsstahl on 2015-09-30 and Filed Under: tools
While I was working on my last post, I experimented with some visualizations that I thought might help make my point a bit more clearly. I didn’t end up using them, but the whiteboard exercise that I went through in developing them helped me organize my thoughts, and, I believe, resulted in a better article.
Once I had drawn-out things the way I wanted them, I did what many people do with a whiteboard, I took a photo of it for my notes. The image above shows what resulted. As you can see, it isn’t a bad rendering, although certainly not perfect. The words and structure are both clearly visible and easily readable, but there is nothing all that impressive about it on its own. After all, there are a number of apps out there which can convert a photo of a whiteboard to a similar image. The part where it becomes interesting is when you see the original source photo, shown below.
You see, I was working on the post from my hotel room, and my “whiteboard” was the hotel window. Despite all of the background clutter, I didn’t have to do anything special to get the whiteboard image. I just did what I always do, open Office Lens, select whiteboard, and take a picture. The app did the rest. Not only that, but it also, once I saved it, automatically uploaded it to my OneNote so that, by the time I got back to my laptop, I already had a synced copy of it in OneNote ready to be dragged into the appropriate notebook. Plus, since my phone is set to sync my photos to OneDrive, I already had a copy of both the original image, and the whiteboard image, in my OneDrive Camera Roll. All of this is configurable of course. If you want, Office Lens will just save the images to your phone. But for me, the OneNote integration is a huge time-saver.
Oh, and by the way, it can also function as a document and business card scanner. Magic!
Office Lens is a free app from Microsoft that is available on all major phone platforms.