In JavaScript, the destructuring of an object is something common.
const foo = {
a: 1
b: 2
c: 3
};
const {a, b, c } = foo;
console.log(a)
1
Is something like this possigle with KotlinJS React?
interface FooProps : Props {
var a: Int
var b: Int
var c: Int
}
val Foo = FC<FooProps> { props ->
val(a, b, c) = props
...
}
This is not working. It gives me
Destructuring declaration initializer of type FooProps must have a 'component1()' function
Kotlin supports destructuring declarations, however they work in a different way than JavaScript. In particular, you can destructure an object like this:
val (property1, property2, property3, ..., propertyN) = object
assuming that object
contains certain methods:
operator fun component1()
operator fun component2()
operator fun componentN()
Example:
class Person(val name: String, val dateOfBirth: LocalDate) {
operator fun component1(): String = name
operator fun component2(): LocalDate = dateOfBirth
}
val johnDoe = Person("John", LocalDate.of(1980, JANUARY, 1))
val (name, dob) = johnDoe
println("$name -> $dob") // prints John -> 1980-01-01
Use can make use of extension functions to implement this behaviour on classes you don't own. Example:
operator fun String.component1(): Int = this.length
operator fun String.component2(): Char = this.first()
val someString = "Hello, world"
val (length, firstChar) = someString
println("$length -> $firstChar") // prints 12 -> H