The title might sound weird at beginning since many modern libraries or tools are designed to make developers write less code via ways like code generation or reflection. Those libraries are great and convenient to use because we write less code. However in my experience sometimes developers become careless and misuse those libraries by calling them everywhere they could. Eventually the codebase becomes difficult to read and maintain. Here are some examples I have seen many times and would like to share with you.

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In my previous post Kotlin “By” Class Delegation: Favor Composition Over Inheritance I covered using by keyword for class delegations. You can easily reuse and compose existing concrete implementations in your code. In this post I will be going over using the same by keyword for properties and how you can use them to create reusable code and reduce awkward boilerplate code. I will also include some Android specific samples with delegated properties.

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KotlinConf is the first ever conference that is all about the new favorite language Kotlin. The event is held by Jetbrains officially at Pier 27, San Fransisco. It is two day long and you can see many developers from big companies like Google, Gradle, Pivotal, Facebook giving talks or or attending events themselves. I was lucky enough that I purchased my ticket for $99 on the first day they announced the event, and four friends/coworkers of mine went together, making this event even more enjoyable.

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When people ask me why Kotlin over Java, I often say because Kotlin is a better Java. You get more than half of Effective Java implemented for you. In charter 4 of the book, the author lists many items about inheritance because it is very error prone. The most well known item probably would be Item 16: Favor composition over inheritance. To implement that item, Kotlin introduces a special key work by to help you with implementing delegation in a single line.

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A week ago I was thinking of writing a small Kotlin command line tool to read some local json files. I opened IntelliJ and started a kotlin project with gradle. Everything worked just fine. I could compile and run the output jar file until I imported autovalue. Autovalue uses annotation processor to generate model objects, but IntelliJ just would not invoke annotation processing properly so the compilation failed. I did some research and finally made it to work, and I think these tricks are worth to share.

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Eric Lin

A software engineer who does Android, Server(less), and Kotlin development and enjoys learning new technologies

Software Engineer

Mountain View, CA