February 2019 marked the release of ReactiveUI 9 — the cross-platform framework for building GUI applications on the Microsoft .NET platform. ReactiveUI is a tool for tight integration of reactive extensions with the MVVM design pattern. You could familiarize yourself with the framework via a series of videos or the welcome page of the documentation. The ReactiveUI 9 update includes numerous fixes and improvements, but probably the most crucial and interesting one is integration with the DynamicData framework, allowing you to work with dynamic collections in Reactive fashion. Let’s find out what we can use DynamicData for and how this powerful reactive framework works under the hood!

This week I spent coding my very first public pet-app based on Telegram chat bot which acts as a Bitcoin wallet and allows to send and receive tips between Telegram users and other so-called “Lightning Apps”. I assume that you are familiar with Bitcoin & Telegram in general, i’ll try to post short and without deep jump into details. More resources about Bitcoin can be found here and Telegram is simply an instant messenger that allows you to create your custom apps (chat-bots) using their platform.

What are the key points of such app?

• Allows to rate other users ideas and answers with real value instead of
  ‘virtual likes’. This brings online conversation to completely new level
• Real example of working micro-payment app which can act with other entities
  over internet using open protocol
• All the modules are open-source projects and can be easy re-used and adjusted
  for your own project. App does not relay on third-party commercial services.
  Even it falls under e-commerce field, which is currently almost closed, the app
  is based on open solutions.

What are the use-cases?

something like this…

With a variety of new tools and features announced at Android Dev Summit, special attention should be given to the In-App Updates (IAUs) API allowing developers to increase the speed of delivering features, bug-fixes and performance improvements to active users. Since this feature was finally released after Google I/O 2019, in this article I’ll deep dive on IAUs API, describe in details recommended user flows and provide with some code samples. Moreover, I'll share some experience of IAUs integration in the Pandao app, a marketplace platform for Chinese goods.

Code search and navigation are important features of any IDE. In Java, one of the commonly used search options is searching for all implementations of an interface. This feature is often called Type Hierarchy, and it looks just like the image on the right.

It's inefficient to iterate over all project classes when this feature is invoked. One option is to save the complete class hierarchy in the index during compilation since the compiler builds it anyway. We do this when the compilation is run by the IDE and not delegated, for example, to Gradle. But this works only if nothing has been changed in the module after the compilation. In general, the source code is the most up-to-date information provider, and indexes are based on the source code.

Finding immediate children is a simple task if we are not dealing with a functional interface. When searching for implementations of the Foo interface, we need to find all the classes that have implements Foo and interfaces that have extends Foo, as well as new Foo(...) {...} anonymous classes. To do this, it is enough to build a syntax tree of each project file in advance, find the corresponding constructs, and add them to an index.

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

Earlier this week, we released Visual Studio 2019 version 16.1 Preview 1 (see release notes). It’s the first preview of the first update to Visual Studio 2019. If you’re not already set up to get preview releases, then please do that now. The preview channel installs side-by-side with the release channel and they don’t interfere with each other. I highly recommend all extension authors install the preview.

Got the 16.1 preview installed now then? That’s great. Here are some features in it you might find interesting.

Java developers have access to a number of useful tools that help to write high-quality code such as the powerful IDE IntelliJ IDEA, free analyzers SpotBugs, PMD, and the like. The developers working on CUBA Platform have already been using all of these, and this review will show how the project can benefit even more from the use of the static code analyzer PVS-Studio.

ML.NET is an open-source and cross-platform machine learning framework (Windows, Linux, macOS) for .NET developers. Using ML.NET, developers can leverage their existing tools and skillsets to develop and infuse custom AI into their applications by creating custom machine learning models for common scenarios like Sentiment Analysis, Recommendation, Image Classification and more!.

Today we’re announcing the ML.NET 1.0 RC (Release Candidate) (version 1.0.0-preview) which is the last preview release before releasing the final ML.NET 1.0 RTM in 2019 Q2 calendar year.

Soon we will be ending the first main milestone of a great journey in the open that started on May 2018 when releasing ML.NET 0.1 as open source. Since then we’ve been releasing monthly, 12 preview releases so far, as shown in the roadmap below:

In this release (ML.NET 1.0 RC) we have initially concluded our main API changes. For the next sprint we are focusing on improving documentation and samples and addressing major critical issues if needed.

The goal is to avoid any new breaking changes moving forward.

Multithreading

Now let’s talk about thin ice. In the previous sections about IDisposable we touched one very important concept that underlies not only the design principles of Disposable types but any type in general. This is the object’s integrity concept. It means that at any given moment of time an object is in a strictly determined state and any action with this object turns its state into one of the variants that were pre-determined while designing a type of this object. In other words, no action with the object should turn it into an undefined state. This results in a problem with the types designed in the above examples. They are not thread-safe. There is a chance the public methods of these types will be called when the destruction of an object is in progress. Let’s solve this problem and decide whether we should solve it at all.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

Your friendly neighborhood .NET productivity team (aka. Roslyn) focuses a lot on improving the .NET coding experience. Sometimes it’s the little refactorings and code fixes that really improve your workflow. You may have seen many improvements in the previews, but for all of you who were eagerly awaiting the GA release here’s a few features you may enjoy!

It is a new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

0_0

0_0 is a totally valid Python expression.

Christmas has always been one of my favourite times of the year. For me, Christmas is a season that brings so much love, laughter, happiness, and other magical things into our lives.

I was born and raised in Spain, more specifically in Tenerife, a sunny subtropical island in the middle of the Atlantic Ocean just off the African coast. I have to say that Christmas in Tenerife is very different to my the last two Christmases I’ve spent in London since joining Badoo.

One amazing plus of living in London is that I have got to see snow for the first time in my life, real snowflakes falling from the sky. Just incredible!

Talking of snowflakes, I have an interesting story to tell you about something that happened to me one day in the office the last Christmas.  It was right before I was heading home to Tenerife to spend a few days with my family.

It just so happened that last December I’d been assigned a very interesting ticket with the following description

Span<T> usage examples

A human by nature cannot fully understand the purpose of a certain instrument until he or she gets some experience. So, let’s turn to some examples.

ValueStringBuilder

One of the most interesting examples in respect to algorithms is the ValueStringBuilder type. However, it is buried deep inside mscorlib and marked with the internal modifier as many other very interesting data types. This means we would not find this remarkable instrument for optimization if we haven’t researched the mscorlib source code.

What is the main disadvantage of the StringBuilder system type? Its main drawback is the type and its basis — it is a reference type and is based on char[], i.e. a character array. At least, this means two things: we use the heap (though not much) anyway and increase the chances to miss the CPU cash.

Another issue with StringBuilder that I faced is the construction of small strings, that is when the resulting string must be short e.g. less than 100 characters. Short formatting raises issues on performance.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

SafeHandle / CriticalHandle / SafeBuffer / derived types

I feel I’m going to open the Pandora’s box for you. Let’s talk about special types: SafeHandle, CriticalHandle and their derived types.

This is the last thing about the pattern of a type that gives access to an unmanaged resource. But first, let’s list everything we usually get from unmanaged world:

The first and obvious thing is handles. This may be an meaningless word for a .NET developer, but it is a very important component of the operating system world. A handle is a 32- or 64-bit number by nature. It designates an opened session of interaction with an operating system. For example, when you open a file you get a handle from the WinApi function. Then you can work with it and do Seek, Read or Write operations. Or, you may open a socket for network access. Again an operating system will pass you a handle. In .NET handles are stored as IntPtr type;

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

Dmitry Pichulin, known under the nick «deemru», won the game Fhloston Paradise, developed by Tradisys on the Waves blockchain.

The winner of Fhloston Paradise was supposed to be the player paying the very last stake during a 60-block period, before any other player could pay their stake and reset the counter to zero. The winner would collect all stakes paid by other players.

Dmitry's winning recipe was the bot Patrollo, which he created. The bot paid just eight 1 WAVES stakes for Dmitry and eventually won him 4,700 WAVES ($13,100). In this interview, Dmitry discusses his bot and prospects of blockchain games.

Disposable pattern (Disposable Design Principle)

I guess almost any programmer who uses .NET will now say this pattern is a piece of cake. That it is the best-known pattern used on the platform. However, even the simplest and well-known problem domain will have secret areas which you have never looked at. So, let’s describe the whole thing from the beginning for the first-timers and all the rest (so that each of you could remember the basics). Don’t skip these paragraphs — I am watching you!

If I ask what is IDisposable, you will surely say that it is

public interface IDisposable
{
    void Dispose();
}

What is the purpose of the interface? I mean, why do we need to clear up memory at all if we have a smart Garbage Collector that clears the memory instead of us, so we even don’t have to think about it. However, there are some small details.

This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.

Also, if you want thank us, the best way you can do that is to give us a star on github or to fork repository github/sidristij/dotnetbook.

• First of all, you can read this article in russian here.

One evening, I was reading Mastering regular expressions by Jeffrey Friedl , I realized that even if you have all the documentation and a lot of experience, there could be a lot of tricks developed by different people and imprisoned for themselves. All people are different. And techniques that are obvious for certain people may not be obvious to others and look like some kind of weird magic to third person. By the way, I already described several such moments here (in russian) .

For the administrator or the user the command line is not only a tool that can do everything, but also a highly customized tool that could be develops forever. Recently there was a translated article about some useful tricks in CLI. But I feel that the translator do not have enough experience with CLI and didn't follow the tricks described, so many important things could be missed or misunderstood.

Under the cut — a dozen tricks in Linux shell from my personal experience.

It has been three months since 2018 had ended. For many, it has just flew by, but for us, PVS-Studio developers, it was quite an eventful year. We were working up a sweat, fearlessly competing for spreading the word about static analysis and were searching for errors in open source projects, written in C, C++, C#, and Java languages. In this article, we gathered the top 10 most interesting of them right for you!

What's new in CUBA 7

Three years ago we announced the second publicly available major version of the framework. CUBA 6 was the game-changing version — the licensing was turned from proprietary to Apache 2.0. Those days we couldn't even guess where it was going to bring the framework in long term. CUBA community started to grow exponentially, so we have learned a lot of possible (and sometimes impossible) ways of how developers use the framework. Now we are happy to announce CUBA 7, which, we hope, will make development more coherent and joyful for all community members from those just starting their journey in CUBA and Java to skilled enterprise developers and Java experts.

It is new selection of tips and tricks about Python and programming from my Telegram-channel @pythonetc.

Previous publications.

Structures comparing

Sometimes you want to compare complex structures in tests ignoring some values. Usually, it can be done by comparing particular values with the structure: