Source
[deleted]•

[deleted]

8
ProxusChan•

His argument doesn't even really hold water because he seems to be operating under a misunderstanding. He says no one would name sealed classes like that, which, sure, but they're classes, not constants. He then shows code with a few constants, in which he used the SCREAMING_SNAKE_CASE style for the constants, so he seems to be an advocate of doing that style for constants, but not enum constants. That just creates a very inconsistent style, and quite frankly, looks ugly.

10
Astronaut4449•

Use CamelCase, don’t be ashamed. I doubt that anyone names sealed class using the UPPERCASE notation.

Do not compare an enum to a sealed class. Sealed classes can have as many instances as you want whereas enums represent a limited set of instances.

That's why you check for the type when using sealed classes and for identity when using enums.

// type check using sealed class
instance is MySealedClass

// equality or identity check using enum
instance === MyEnum.MY_INSTANCE

The official Kotlin documentation names enum entries with UPPERCASE. I suggest sticking to that.

​

There is catch though - a class can have a single companion object

That might be true, but a class can have multiple named objects:

class MyClass {
    // namespace MyObject
    companion object {
        val className = "MyClass"
    }
    
    // namespace MyObject.Numbers
    object Numbers {
        val one = 1
        val two = 2
    }
    
    // namespace MyObject.Chars
    object Chars {
        val a = 'a'
        val b = 'b'
    }
}
4
natandestroyer•

Wow, I didn’t believe so much can be said about enums.

3
Mango1666•
enum class IsTrue {
    Yes,
    No
}

get those pesky booleans out of your life

4
jibmaster•

Good information

3
olavurdj•

On a minor note, I'd refactor your example with sections to make use of ranges instead of your own implementation of it, such that

enum class Section(@StringRes val title: Int, val from: Int, val to: Int) {
    Dozen(R.string.Section_Dozen, from = 0, to = 10),
    Dozens(R.string.Section_Dozens, from = 11, to = Int.MAX_VALUE),
}

listOf(1, 2, 3, 42).groupBy { number ->
    Section.values().find { it.from <= number && number <= it.to }
}

becomes

enum class Section(@StringRes val title: Int, val range: IntRange) {
    Dozen(R.string.Section_Dozen, 0..10),
    Dozens(R.string.Section_Dozens, 11..Int.MAX_VALUE),
}

listOf(1, 2, 3, 42).groupBy { number ->
    Section.values().find { it.range.contains(number) }
}
2