A common use case for static functions is grouping some utility functions inside a class. Kotlin doesn't have a static keyword, but can achieve this kind of functionality with some other language features. Static members belong to a type, and not to an instance of a type. Java has a static keyword that can be applied to class members. The init block will be called when your object gets constructed: Here is how you would declare an object inside a class:įinally, if you need to some kind of initialization of your object, you can do it inside the init block. Nested objects cannot have an inner keyword they cannot access members from the outer class. Kotlin also allows objects to be declared inside classes then, they become nested singletons. Here is an object that implements the Runnable interface: Objects can have properties and functions they can also implement interfaces and extend other classes. Other than not having a constructor, there aren't any differences from normal classes. Here's how to call a function from an object: If you need to access a member from an object, you can do so by first accessing the object type and then the member you wish to invoke. Since the compiler creates an instance for you, if you tried to declare a constructor or create an instance yourself, you'd get a compiler error. Notice how we haven't defined a constructor. This will both declare a Singleton class and create an instance of it. But, Kotlin has language support for creating singletons with the object keyword. In other languages, you would have to implement this pattern manually, making sure that only one instance of your type gets created. Sometimes, your program has to have only one instance of a certain type. Creates an instance of the object on the fly, the same as Java's anonymous inner classes. These members can't require an instance of the outer class.

Defines a nested class that can hold members related to the outer containing class. It can be used in three different situations and has three different meanings. Kotlin has an object keyword, which combines both declaring a class and creating an instance of it in one action.

Kotlin any to object