This expressions
To denote the current receiver, you use this
expressions:
In a member of a class,
this
refers to the current object of that class.In an extension function or a function literal with receiver
this
denotes the receiver parameter that is passed on the left-hand side of a dot.
If this
has no qualifiers, it refers to the innermost enclosing scope. To refer to this
in other scopes, label qualifiers are used:
Qualified this
To access this
from an outer scope (a class, extension function, or labeled function literal with receiver) you write this@label
, where @label
is a label on the scope this
is meant to be from:
class A { // implicit label @A inner class B { // implicit label @B fun Int.foo() { // implicit label @foo val a = this@A // A's this val b = this@B // B's this val c = this // foo()'s receiver, an Int val c1 = this@foo // foo()'s receiver, an Int val funLit = lambda@ fun String.() { val d = this // funLit's receiver } val funLit2 = { s: String -> // foo()'s receiver, since enclosing lambda expression // doesn't have any receiver val d1 = this } } } }
Implicit this
When you call a member function on this
, you can skip the this.
part. If you have a non-member function with the same name, use this with caution because in some cases it can be called instead:
fun main() { //sampleStart fun printLine() { println("Top-level function") } class A { fun printLine() { println("Member function") } fun invokePrintLine(omitThis: Boolean = false) { if (omitThis) printLine() else this.printLine() } } A().invokePrintLine() // Member function A().invokePrintLine(omitThis = true) // Top-level function //sampleEnd() }
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https://kotlinlang.org/docs/this-expressions.html