https://grokonez.com/kotlin/kotlin-singleton-object-declaration
Kotlin Singleton with Object Declaration
In object oriented programming, there is a common situation when you want a class to have only one instance. In Java, we usually implement using the Singleton Design Pattern: define a class with a private constructor and a static field holding the only existing instance of that class. This tutorial shows you a way to implement Singleton with Kotlin Object Declaration.
I. Technology
- Java 1.8
- Kotlin 1.1.2
II. Overview
Kotlin provides object declaration feature with keywordobject
.
We use object
keyword in several cases, but they all have the same core idea:
- defines a class, and at the same time
- creates an instance (an object) of that class
Like a class, an object declaration can contain declarations of properties, methods...
object Singleton {
init {
...
}
var a: Int = ...
fun doWork() {
...
}
}
But constructors are not allowed. Object declarations are created immediately at the point of definition, not through constructor. So defining a constructor in this case doesn’t make sense.
Object declarations can also inherit from class
and interface
.
You can call methods and access properties simply:
More at:
https://grokonez.com/kotlin/kotlin-singleton-object-declaration
Kotlin Singleton with Object Declaration
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