Rodrigo Sicarelli — Staff Software Engineer, Kotlin Multiplatform authority, speaker and OSS maintainer.https://rsicarelli.com/en© 2026 Rodrigo Sicarelli — CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/)https://rsicarelli.com/en/blog/claude-code-101-demystifying-language-models/https://rsicarelli.com/en/blog/claude-code-101-demystifying-language-models/In the previous article, we built the entire factory: the evolution from manual production to autonomous machines, the ecosystem of agentic tools, the three pillars (prompt, context, and harness engineering). You know what the factory does, who works in it, and even how much revenue it pulls in.Thu, 09 Apr 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/claude-code-101-introduction-to-agentic-programming/https://rsicarelli.com/en/blog/claude-code-101-introduction-to-agentic-programming/September 2025. I was leading a critical dependency upgrade on a mobile app with millions of users. The kind of change that breaks tests in a cascade. The deadline was October: if it wasn't ready, the app wouldn't ship to the store.Mon, 06 Apr 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/fakt-automating-the-fake-over-mock-pattern-amh/https://rsicarelli.com/en/blog/fakt-automating-the-fake-over-mock-pattern-amh/Kotlin testing has a problem that gets worse the more successful your project becomes.Wed, 25 Feb 2026 00:00:00 GMThttps://rsicarelli.com/en/blog/the-hidden-cost-of-default-hierarchy-templates-in-kotlin-multiplatform/https://rsicarelli.com/en/blog/the-hidden-cost-of-default-hierarchy-templates-in-kotlin-multiplatform/The Default Hierarchy Template in KMP projects is a great way to reduce boilerplate code and start working quickly. However, it came with an unexpected…Sun, 02 Nov 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-modularizacao-no-kmp/https://rsicarelli.com/en/blog/kmp-102-modularizacao-no-kmp/In the last article we dug into the quirks of code exported to Objective-C headers, along with the best practices for what to export.Fri, 07 Mar 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-otimizando-a-exportacao-do-kotlin-para-o-obj-cswift/https://rsicarelli.com/en/blog/kmp-102-otimizando-a-exportacao-do-kotlin-para-o-obj-cswift/In the last post, we learned how to use Kotlin code in Swift. We covered a few techniques to improve the code exported to Swift, and how annotations like @HiddenFromObjC and @HidesFromObjC control the visibility of code in Swift.Sat, 18 Jan 2025 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-utilizando-codigo-kotlin-no-swift/https://rsicarelli.com/en/blog/kmp-102-utilizando-codigo-kotlin-no-swift/In the last post, we learned how to create an XCFramework from Kotlin code and explored some characteristics of the generated build types.Fri, 11 Oct 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-caracteristicas-do-xcframework-no-kmp/https://rsicarelli.com/en/blog/kmp-102-caracteristicas-do-xcframework-no-kmp/In the previous post, we learned how Kotlin/Native exports a collection of .frameworks in the XCFramework format.Sun, 21 Jul 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-102-xcframework-para-devs-kmp/https://rsicarelli.com/en/blog/kmp-102-xcframework-para-devs-kmp/Welcome to the KMP-102 series. We dig deeper into Kotlin Multiplatform concepts, learning more about how to integrate our Kotlin code into iOS and beyond.Wed, 29 May 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-alias-para-importacao-import-alias/https://rsicarelli.com/en/blog/kotlin-koans-br-alias-para-importacao-import-alias/When importing a class or function, you can give it a different name by adding as NewName after the import directive. This can be useful when…Sat, 06 Apr 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-extension-functions-e-properties-funcoes-e-propriedades-estendidas/https://rsicarelli.com/en/blog/kotlin-koans-br-extension-functions-e-properties-funcoes-e-propriedades-estendidas/Implement the extension functions Int.r() and Pair.r() so they convert an Int and a Pair into a RationalNumber.Sat, 06 Apr 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-nomeados/https://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-nomeados/Make the joinOptions() function return the list in JSON format (for example, [a, b, c]) by specifying only two arguments.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-padrao/https://rsicarelli.com/en/blog/kotlin-koans-br-argumentos-padrao/Imagine you have several overloads of foo() in your favorite language. You can replace them all with a single function in Kotlin.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-classes-de-dados-data-classes/https://rsicarelli.com/en/blog/kotlin-koans-br-classes-de-dados-data-classes/Rewrite the following code in Kotlin, then add the data modifier. A beginner-friendly look at Kotlin classes and data classes.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-classes-seladas/https://rsicarelli.com/en/blog/kotlin-koans-br-classes-seladas/Reuse your solution from the previous task, but replace the interface with a sealed interface. That way you no longer need the else branch in the when expression.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-lambdas/https://rsicarelli.com/en/blog/kotlin-koans-br-lambdas/Pass a lambda to the any function to check whether the collection contains an even number.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-modelos-de-string/https://rsicarelli.com/en/blog/kotlin-koans-br-modelos-de-string/The pattern below matches a date in the format 13.06.1992 (two digits, a dot, two digits, a dot, four digits):Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-ola-mundo/https://rsicarelli.com/en/blog/kotlin-koans-br-ola-mundo/Change the code so that the start function returns the string "OK".Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-strings-com-tres-aspas/https://rsicarelli.com/en/blog/kotlin-koans-br-strings-com-tres-aspas/Swap the trimIndent call for trimMargin, setting # as the prefix value, so the resulting string no longer contains the prefix character.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipagem-inteligente/https://rsicarelli.com/en/blog/kotlin-koans-br-tipagem-inteligente/Rewrite the given code using Kotlin smart casts and the when expression.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipo-nenhum-nothing/https://rsicarelli.com/en/blog/kotlin-koans-br-tipo-nenhum-nothing/Specify the Nothing return type for the failWithWrongAge function.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-koans-br-tipos-anulaveis/https://rsicarelli.com/en/blog/kotlin-koans-br-tipos-anulaveis/Rewrite the following code so that it uses only a single if expression, and learn how Kotlin handles nullable types safely.Thu, 07 Mar 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-explorando-as-dependencias-internas-e-externas-no-kmp/https://rsicarelli.com/en/blog/kmp-101-explorando-as-dependencias-internas-e-externas-no-kmp/In previous articles, we established a foundation in Kotlin Multiplatform (KMP) and how it compiles to multiple platforms.Sat, 27 Jan 2024 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-como-compartilhar-codigo-no-kmp-conectando-plataformas-com-expect-e-actual/https://rsicarelli.com/en/blog/kmp-101-como-compartilhar-codigo-no-kmp-conectando-plataformas-com-expect-e-actual/Over the last few articles, we dug into the inner workings of Kotlin Multiplatform: its paradigm, the compiler architecture, the source sets, the development environment, building and running a sample project, and the essential role of Gradle.Wed, 13 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-aprendendo-sobre-o-uso-do-gradle-no-kotlin-multiplataforma/https://rsicarelli.com/en/blog/kmp-101-aprendendo-sobre-o-uso-do-gradle-no-kotlin-multiplataforma/In the last article, we created a project using the KMP Wizard and, with little effort, ran our app on Android, iOS, and Desktop devices.Fri, 01 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-criando-e-executando-seu-primeiro-projeto-multiplataforma-no-fleet/https://rsicarelli.com/en/blog/kmp-101-criando-e-executando-seu-primeiro-projeto-multiplataforma-no-fleet/Over the last few articles we covered key KMP concepts, from the multiplatform paradigm to setting up the environment.Fri, 01 Dec 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kmp-101-guia-pratico-para-configurar-e-entender-o-ambiente-no-kotlin-multiplataforma/https://rsicarelli.com/en/blog/kmp-101-guia-pratico-para-configurar-e-entender-o-ambiente-no-kotlin-multiplataforma/Software development is a complex process that demands not only skill and creativity, but also a well-configured development environment.Wed, 29 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-dominando-os-principios-dos-source-sets/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-dominando-os-principios-dos-source-sets/In the last article (🔗 KMP 101: Understanding How Kotlin Compiles for Multiple Platforms), we learned about the frontend, IR, and backend of the Kotlin compiler.Fri, 24 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-entendendo-como-o-kotlin-compila-para-multiplas-plataformas/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-entendendo-como-o-kotlin-compila-para-multiplas-plataformas/In the last post (🔗 KMP 101: An Introduction to the multiplatform paradigm), we explored the multiplatform paradigm and how KMP stands out in the ecosystem.Tue, 21 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/kotlin-multiplataforma-101-introducao-ao-paradigma-da-multiplataforma/https://rsicarelli.com/en/blog/kotlin-multiplataforma-101-introducao-ao-paradigma-da-multiplataforma/We use a wide range of apps every day on phones, watches, TVs, and computers, all part of a broad digital ecosystem.Tue, 14 Nov 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-0-introducao-a-serie/https://rsicarelli.com/en/blog/android-plataforma-parte-0-introducao-a-serie/Android development is a constant stream of new things: new devices, SDK updates, and an endless variety of libraries and tools that ship every single day.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-1-modularizacao/https://rsicarelli.com/en/blog/android-plataforma-parte-1-modularizacao/Efficiency matters in modern software projects. This article covers modularization in Kotlin/Android projects, the vital role Gradle plays in speeding up builds, and the challenges of managing multiple modules.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-10-customizacao-dos-modulos/https://rsicarelli.com/en/blog/android-plataforma-parte-10-customizacao-dos-modulos/In the last article we explored CommonsExtension to remove duplication from our configuration.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-11-criando-uma-dsl-para-customizar-as-novas-opcoes/https://rsicarelli.com/en/blog/android-plataforma-parte-11-criando-uma-dsl-para-customizar-as-novas-opcoes/In the previous article, we parameterized the arguments of applyAndroidApp() and appyAndroidLibary() with models.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-12-otimizando-tempo-de-compilacao-para-bibliotecas-android/https://rsicarelli.com/en/blog/android-plataforma-parte-12-otimizando-tempo-de-compilacao-para-bibliotecas-android/🌱 Branch: 12/improving-android-library-build-time 🔗 Repository:...Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-13-incluindo-modulos-puro-jvm/https://rsicarelli.com/en/blog/android-plataforma-parte-13-incluindo-modulos-puro-jvm/In the last article we sped up Android module builds by turning off several Android Gradle Plugin (AGP) features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-14-aderindo-a-funcionalidades-experimentais-do-compilador-do-kotlin/https://rsicarelli.com/en/blog/android-plataforma-parte-14-aderindo-a-funcionalidades-experimentais-do-compilador-do-kotlin/In the last article we extended our platform with the ability to declare JVM modules.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-15-cuidando-do-codigo-com-detekt-klint-e-spotless/https://rsicarelli.com/en/blog/android-plataforma-parte-15-cuidando-do-codigo-com-detekt-klint-e-spotless/In the last article we covered how our platform lets different modules opt into experimental features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-16-consideracoes-finais/https://rsicarelli.com/en/blog/android-plataforma-parte-16-consideracoes-finais/Over the last articles, we built a platform from scratch, learning and applying several concepts with the goal of making multi-module Kotlin apps more flexible and scalable.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-2-inicio-do-projeto/https://rsicarelli.com/en/blog/android-plataforma-parte-2-inicio-do-projeto/In this post we explore a starter project, understand the challenges of maintaining build.gradle.kts files, and discover how Gradle Composite Builds can help along the way.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-3-compartilhando-scripts-do-gradle/https://rsicarelli.com/en/blog/android-plataforma-parte-3-compartilhando-scripts-do-gradle/In the previous article, we understood the challenges a multi-module project brings: maintaining and reusing Gradle files. Let us get a better grasp on how to solve this problem by looking at two concepts: buildSrc and Composite Builds.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-4-composite-build-lgk/https://rsicarelli.com/en/blog/android-plataforma-parte-4-composite-build-lgk/In the previous articles we saw why modularity matters and why Composite Builds are the right choice for scaling Kotlin projects.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-5-simplificando-gradle-init/https://rsicarelli.com/en/blog/android-plataforma-parte-5-simplificando-gradle-init/In the previous article, we set up our platform with build-logic and registered the greeting task in the main project.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-6-version-catalog/https://rsicarelli.com/en/blog/android-plataforma-parte-6-version-catalog/In the previous post, we optimized our platform and got it ready for more features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-7-decorando-o-modulo-app/https://rsicarelli.com/en/blog/android-plataforma-parte-7-decorando-o-modulo-app/In the previous article, we got our platform ready to take on new features.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-8-decorando-os-modulo-library/https://rsicarelli.com/en/blog/android-plataforma-parte-8-decorando-os-modulo-library/In the last post, we introduced the first decoration in the Platform and set up our entire app module using the Kotlin DSL.Wed, 27 Sep 2023 00:00:00 GMThttps://rsicarelli.com/en/blog/android-plataforma-parte-9-unificando-a-application-e-library-extensions-com-a-common-extension/https://rsicarelli.com/en/blog/android-plataforma-parte-9-unificando-a-application-e-library-extensions-com-a-common-extension/In the last post, we managed to extract the configuration logic for our library modules.Wed, 27 Sep 2023 00:00:00 GMT