¿Cómo agrego un constructor secundario a Kotlin?

How do I add a secondary constructor to Kotlin?

To do so you need to declare a secondary constructor using the constructor keyword. If you want to use some property inside the secondary constructor, then declare the property inside the class and use it in the secondary constructor. By doing so, the declared variable will not be accessed inside the init() block.

Secondary Constructor A class in Kotlin can have at most one primary constructor, and one or more secondary constructors. The primary constructor initializes the class, while the secondary constructor is used to initialize the class and introduce some extra logic.

Creating multiple constructors for Data classes in Kotlin

1. Data classes in Kotlin are immutable and it’s easy enough to create a constructor for a data class with multiple fields.
2. Another option is the @JvmOverloads annotation which generates multiple constructors based on the arguments in the constructor.

In Kotlin, constructor is a block of code similar to method. Constructor is declared with the same name as the class followed by parenthesis ‘()’….Primary constructor with initializer block

1. class myClass(name: String, id: Int) {
2. val e_name: String.
3. var e_id: Int.
4. init{
5. e_name = name.
6. e_id = id.
7. println(“Name = ${e_name}”)

In Kotlin we are not allowed to extend multiple superclasses. Multiple-inheritance is achieved by giving concrete functions to interfaces. Now the amount of boilerplate required to achieve this is reduced to a single line.

Before we proceed, I must note that because classes can have state and initialization logic (including side-effects), Kotlin does not allow true multiple inheritance as that could cause havoc in slightly more complex class hierarchies (it does allow declaring properties and implementing methods in interfaces, though.

If you are not defining the constructor, then the compiler will add constructor known as default constructor. Unlike Java, or any other object-oriented language, Kotlin has two types of constructor: Primary Constructor. Secondary Constructor. But it is not necessary to add secondary constructor also.

In primary constructor we are defining the variable but in the secondary constructor age is being used as a parameter. NOTE: In Kotlin you cannot declare the properties inside the secondary constructor. You have to define the properties inside the body of the class. Time to show via code.

This init () block is executed just after the creation of an object. this keyword is used to refer to the variables of the class or any block. If you have the same variable name in the class property and in the constructor then by using this keyword you can remove the confusion of the compiler.

With the rest of the class being the same, this annotation allows the Kotlin class to be used in Java code. Content created by Alvin Alexander and released under this license.