Hi, my name is Michael Kapelko. I have been developing software professionally for more than 10 years. I develop games and game development tools in my spare time.
This article describes my first durable application for desktop PCs: PSKOV static site generator.
Durability
A durable application is an application that functions without a single change on operating systems released in years 2010-2030. In other words, a durable application has backward compatibility of 10 years and has the stability to run for 10 years. Actually, PSKOV runs even under Windows 2000, so PSKOV has backward compatibility of 19 years.
User interfaces of modern enterprise applications are quite complex. You, as a developer, often need to implement in-app navigation, validate user input, show or hide screens based on user preferences. For better UX, your app should be capable of saving state to the disk when the app is suspending and of restoring state when the app is resuming.
ReactiveUI provides facilities allowing you to persist application state by serializing the view model tree when the app is shutting down or suspending. Suspension events vary per platform. ReactiveUI uses the Exit event for WPF, ActivityPaused for Xamarin.Android, DidEnterBackground for Xamarin.iOS, OnLaunched for UWP.
In this tutorial we are going to build a sample application which demonstrates the use of the ReactiveUI Suspension feature with Avalonia — a cross-platform .NET Core XAML-based GUI framework. You are expected to be familiar with the MVVM pattern and with reactive extensions before reading this note. Steps described in the tutorial should work if you are using Windows 10 or Ubuntu 18 and have .NET Core SDK installed. Let's get started! Source code of the app described in this tutorial is available on GitHub.
if constexpr and generic lambdas so that code could use the type if it is defined, while still being accepted by the compiler (and being discarded) if the type is not defined.struct all the time.struct technique with an unqualified name. You can’t use it to probe a type that you didn’t import into the current namespace.
Some time ago, in a discussion on one of SObjectizer's releases, we were asked: "Is it possible to make a DSL to describe a data-processing pipeline?" In other words, is it possible to write something like that:
A | B | C | D
and get a working pipeline where messages are going from A to B, and then to C, and then to D. With control that B receives exactly that type that A returns. And C receives exactly that type that B returns. And so on.
It was an interesting task with a surprisingly simple solution. For example, that's how the creation of a pipeline can look like:
auto pipeline = make_pipeline(env, stage(A) | stage(B) | stage(C) | stage(D));Or, in a more complex case (that will be discussed below):
auto pipeline = make_pipeline( sobj.environment(),
stage(validation) | stage(conversion) | broadcast(
stage(archiving),
stage(distribution),
stage(range_checking) | stage(alarm_detector{}) | broadcast(
stage(alarm_initiator),
stage( []( const alarm_detected & v ) {
alarm_distribution( cerr, v );
} )
)
) );In this article, we'll speak about the implementation of such pipeline DSL. We'll discuss mostly parts related to stage(), broadcast() and operator|() functions with several examples of usage of C++ templates. So I hope it will be interesting even for readers who don't know about SObjectizer (if you never heard of SObjectizer here is an overview of this tool).
<=>. There was a post awhile back by our very own Simon Brand detailing some information regarding this new operator along with some conceptual information about what it is and does. The goal of this post is to explore some concrete applications of this strange new operator and its associated counterpart, the operator== (yes it has been changed, for the better!), all while providing some guidelines for its use in everyday code.
\ symbol in regular string have special meaning. \t is tab character, \r is carriage return and so on.r'\t' is just backslash and t.' inside r'...'. However, it still can be escaped by \, but \ is preserved in the string:Beginning with C# 8.0 on .NET Core 3.0, you can define an implementation when you declare a member of an interface. The most common scenario is to safely add members to an interface already released and used by innumerable clients.
In this tutorial, you'll learn how to:
I don’t care what your dragon’s said, it’s a lie. Dragons lie. You don’t know what’s waiting for you on the other side.This article is based on the post in the Krister Walfridsson’s blog, “Why undefined behavior may call a never called function?”.
Michael Swanwick, The Iron Dragon’s Daughter
SObjectizer is a rather small C++ framework that simplifies the development of multithreaded applications. SObjectizer allows a developer to use approaches from Actor, Publish-Subscribe and Communicating Sequential Processes (CSP) models. It's an OpenSource project that is distributed under BSD-3-CLAUSE license.
SObjectizer has a long history. SObjectizer itself was born in 2002 as SObjectizer-4 project. But it was based on ideas from previous SCADA Objectizer that was developed between 1995 and 2000. SObjectizer-4 was open-sourced in 2006, but its evolution was stopped soon after that. A new version of SObjectizer with the name SObjectizer-5 was started in 2010 and was open-sourced in 2013. The evolution of SObjectizer-5 is still in progress and SObjectizer-5 has incorporated many new features since 2013.
SObjectizer is more or less known in the Russian segment of the Internet, but almost unknown outside of the exUSSR. It's because the SObjectizer was mainly used for local projects in exUSSR-countries and many articles, presentations, and talks about SObjectizer are in Russian.
Multithreading is used in Parallel computing as well as in Concurrent computing. But there is a big difference between Parallel and Concurrent computing. And, as a consequence, there are tools targeted Parallel computing, and there are tools for Concurrent computing, and they are different.