Tag: Learning Kotlin

149: Learning Kotlin: inline classes and Type driven design

In this quick fragment, Kaushik talks about the new Kotlin 1.3 experimental feature “inline classes” and how it helps with Type driven design.

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Type driven design resources

Kotlin KEEP

vs typealias

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136: Kotlin Extension Functions

In this fragment episode, Donn talks about Kotlin extension functions. He discusses what they are, how to build them, why they’re useful, how to organize them, visibility and how to call them Java and much more.

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Show Notes

`

import android.view.View

fun View.gone() {
    this.visibility = View.GONE
}

fun View.visible() {
    this.visibility = View.VISIBLE
}

`

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092: Learning Kotlin – dealing with static-ness and (companion) objects costs

In this second episode of our learning Kotlin series, we talk about Kotlin’s support for static members or … lack thereof. Kotlin as a language was designed so that there’s no such thing as a “static member” in a class but there are times when having static members can be useful.

So what do we do in those cases? do we just avoid static members? are there better alternatives? what are the costs with some of these approaches?

Listen on to find out more!

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Show Notes

Static alternatives

Cost of approaches

Look at the end of these notes for code snippets

Misc:

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Code snippets

Cost effectiveness

// ----------------------------------------
// THIS IS BAD
class Foo {
    companion object {
        val myVar = "testing"
    }
}

// calling from Kotlin
Foo.myVar

// calling from Java
Foo.Companion.getMyVar();  // yuck

// ----------------------------------------
// THIS IS OK

// notice the Jvm annotation
class Foo {
    companion object {
        @JvmField val myVar = "testing"
    }
}

// calling from Kotlin
Foo.myVar

// calling from Java
Foo.myVar; 

// ----------------------------------------
// THIS IS AWESOME

// notice the const keyword
class Foo {
    companion object {
        const val myVar = "testing"
    }
}

// calling from Kotlin
Foo.myVar

// calling from Java 
Foo.myVar; 
// compiler additionally inlines this

// myVar is not a primitive or String?
// use @JvmField or @JvmStatic for methods

Package level options

// inside BottomSheetView.Kt
class BottomSheetView {
    companion object {
        const val BOTTOM_SHEET_ANIMATION_TIMING = 500L
    }

    // ...
}


// accessed as:
animation.setTiming(BottomSheetView.BOTTOM_SHEET_ANIMATION_TIMING)

// ----------------------------------------
// INSTEAD DO THIS

// inside BottomSheetView.Kt
const val BOTTOM_SHEET_ANIMATION_TIMING = 500L

class BottomSheetView {
    // ...
}

// accessed as:
animation.setTiming(BottomSheetViewKt.BOTTOM_SHEET_ANIMATION_TIMING)

089: Learning Kotlin – Properties a first class language feature

In this mini Fragment, KG talks about his journey learning Kotlin as a newb. Given that Kotlin is most likely going to be the de-facto language for most developers, it makes sense to deepen our understanding of the language (as we have strived with Java over the years).

“Properties” in Kotlin are a first class language feature. But what does that actually mean? What are the nifty features we get with properties? How are these resolved from a Java class when there’s potential a name clash? What are some other gotchas and learnings from using properties? Listen on to find out:

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