Execute Kotlin Scripts with Gradle

Execute Kotlin Scripts with Gradle

Gradle, Kotlin, Software Development, Teaching, Tutorial
Organize Kotlin Scripts as Gradle tasks In this article, you will learn how you can organize multiple Kotlin scripts as Gradle tasks and make them easily executable this way. I've found a discussion about this here. Somebody wanted to execute Kotlin scripts with Gradle build scripts which is, of course, possible by using kotlinc as shown in this (Groovy) build script. This doesn't look very pretty though, and, as described in the corresponding thread, isn't very performant and manageable. Another solution would be to use Gradle scripts written with the Kotlin DSL and define custom tasks within a build.gradle.kts file, which obviously can hold and run Kotlin code naturally: // build.gradle.kts // // Execute Kotlin task with: gradle -q foo task("foo") { group = "com.kotlinexpertise" description = "my foo task"…
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From Java Builders to Kotlin DSLs

From Java Builders to Kotlin DSLs

Android, Java, Kotlin, Tutorial
From Java Builders to Kotlin DSLs Introduction DSLs - Domain Specific Languages - are an ever trending topic in Kotlin circles. They allow us to flex some of the most exciting language features while accomplishing more readable and maintainable solutions in our code. Today I'd like to show you how to implement a certain kind of DSL - we're going to be wrapping an existing Java Builder in Kotlin. No doubt you've come across the builder pattern in Java before, for example if you're an Android developer, you must've used an AlertDialog.Builder, an OkHttpClient.Builder, or a Retrofit.Builder at some point. Wrapping a builder like this is a good exercise in just pure DSL design. All you have to worry about is designing the API you provide with your wrapper, since…
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Android KTX – Android development with Kotlin

Android KTX – Android development with Kotlin

Android, Kotlin, Software Development, Teaching, Tutorial
Introduction Android KTX is an open source library or set of functionalities designed to make the Android development with Kotlin even more pleasant. You can find its website here. The abbreviation KTX stands for Kotlin Extensions, so this library is basically a set of extension functions, extension properties and other top-level functions. In this article, we take a look at what's inside this library and how we can take advantage of it. This library's goal is not to add new features to the existing Android APIs, but rather make those APIs easier to use by leveraging the features of the Kotlin language. Structure of Android KTX A very important thing to note at the beginning is that Android KTX provides functionalities which would be added to many individual projects by…
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Kotlin Nullability Features

Kotlin Nullability Features

Functional Programming, Java, Kotlin, Software Development, Teaching, Tutorial
Null-Safe Programming - The Kotlin Way Disclaimer: This ktor article was originally published in the Dzone Java Guide 2018, which can be downloaded here. In this article, we will review the problems that may be caused by null pointers and how to avoid them in Java. After that, the article demonstrates how Kotlin nullability features work and how they improve your code. As Java developers, we're very accustomed to NullPointerExceptions (NPE) that are thrown at the runtime of an application. This almost always happens unintentionally in consequence of a bug, which is based on unrecognized references to null. The null reference is often used to indicate absent values, which isn't obvious to the programmer in many cases. Although Java relies on strong static typing, it doesn't let you distinguish between…
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Why you should start contributing to StackOverflow

Why you should start contributing to StackOverflow

Kotlin, Software Development, Teaching, Tutorial
A little History A few years back, when I started getting into programming, I googled a lot of the problems I was facing during the day and mostly found my answers on StackOverflow. The place that every programmer is kind of dependent on. I still face problems and I still find my answers on StackOverflow. Something has changed, though. I don't only consume content on the website but also contribute to it. Until May 2017, I didn't even have an account on StackOverflow. At this time, I was getting interested in knowing how it's like to answer questions instead of just reading them. I enjoyed helping others to solve their Kotlin-related problems ever since I started learning the Kotlin programming language. This was my initial motivation for creating an account and…
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Publish Kotlin Library on Bintray using Gradle Kotlin DSL and Travis CI

Publish Kotlin Library on Bintray using Gradle Kotlin DSL and Travis CI

Gradle, Java, Kotlin, Software Development, Tutorial
Distribute a Library on Bintray using Gradle Kotlin DSL In my latest blog post, published a few weeks back, I informed about the usage of the Gradle Kotlin DSL and how it helps with describing build scripts. In another earlier post, I introduced a small library that can be utilized for simplifying the creation of TLS/SSL sockets using a custom Kotlin DSL: SeKurity. In this post, we'll investigate how such a library can be made available to others that actually want to make use of it inside other projects. Ultimately, it should be possible to list the SeKurity library as a simple dependency in a build script like Maven or Gradle. Since the library itself is already backed by Gradle, I'll show a way of publishing the resulting artifacts at…
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Kotlin Tutorial – Quick Reference – Getting Started with Kotlin

Kotlin Tutorial – Quick Reference – Getting Started with Kotlin

Functional Programming, Kotlin, Software Development, Tutorial
Introduction Disclaimer: This reference has originally been published as a DZone Refcard. Kotlin has become one of the most popular JVM languages in the past few months. One special reason is that it experienced a lot of attention in the Android community after Google made Kotlin an official language for Android development. Kotlin is being developed by JetBrains, who are responsible for the most famous IDEs out there, most notably IntelliJ IDEA. Nevertheless, it's an open source language, which can be found on GitHub. The language is said to be very concise, safe in terms of error frequency, interoperable with Java and also offers many features that enable functional programming, writing type-safe DSLs and much more. Beside the JVM, Kotlin can compile for most Android versions, down to machine code…
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The Power of Gradle Kotlin DSL

The Power of Gradle Kotlin DSL

Functional Programming, Gradle, Kotlin, Software Development, Tutorial
-The following is based on Gradle 4.3.1- A few weeks ago I started migrating most of my Groovy-based gradle.build scripts to Kotlin-backed gradle.build.kts scripts using the Kotlin DSL. Why would I do that? Kotlin is my language of choice and I love the idea of using a single language to do all my work. I never learned programming with Groovy and only know the bloody basics, which always makes me think: "This can't be the best way to do things...". Kotlin, on the other hand, is a language I use on a daily basis and therefore I know how to use the language appropriately. Additionally, Kotlin is a statically-typed language, whereas Groovy isn't. IDEs are having hard times offering code completion and error detection at compile time when a Groovy…
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Kotlin Reified Types in Inline Functions

Kotlin Reified Types in Inline Functions

Functional Programming, Kotlin, Software Development, Tutorial
Kotlin Reified Types in Inline Functions I've noticed that many people haven't ever heard of reified types or have problems understanding what they are and what they do. Therefore this little post is intended to bring some light into the darkness of Kotlin's reified types. Starting situation fun <T> myGenericFun(c: Class<T>) In an ordinary generic function like myGenericFun, you can't access the type T because it is, like in Java, erased at runtime and thus only available at compile time. Therefore, if you want to use the generic type as a normal Class in the function body you need to explicitly pass the class as a parameter like the parameter c in the above example. That's correct and works fine but makes it a bit unsightly for the caller. Inlined…
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Kotlin Operator Overloading – Working by Convention

Kotlin Operator Overloading – Working by Convention

Functional Programming, Kotlin, Software Development, Tutorial
Kotlin Operator Overloading and Conventions Introduction Kotlin supports a technique called conventions, everyone should be familiar with. For example, if you define a special method plus in your class, you can use the + operator by convention: Kotlin Operator Overloading. In this article, I want to show you which conventions you can use and I will also provide a few Kotlin code examples that demonstrate the concepts. (more…)
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