How to access primary constructor parameters inside secondary constructor kotlin

Question

I am learning kotlin and I was reading about constructors: primary and secondary.

Here is my question that how should I access primary constructor parameters inside a secondary constructor. I am unable to access but I am not sure why? Why I am not able to access it directly?
If anyone knows please help me understand this concept in a better way. Why I am not able to access it?

I have created one demo class with two constructors here is my code:

fun main(args: Array<String>) {

    val person1 = Person("Joe", 25)
    println("First Name = ${person1.firstName}") // working, printing first name 

}

class Person(val firstName: String, var age: Int) {

    constructor(sectionName: String, id: Int, name: String) : this(sectionName,id)  {
        println("Age = ${age}") // not working, no output
    }

}

Or Am I doing anything wrong?

PS: I know I can write init block and assign the parameters to the class variable and it is working as expected.

You're not calling the secondary constructor.

Ryan M
– Ryan M ♦

2020-02-26 08:22:45 +00:00
Commented Feb 26, 2020 at 8:22 — Ryan M
– Ryan M ♦, Commented Feb 26, 2020 at 8:22
What a silly mistake thank you for pointing out. :)

Harsh Shah
– Harsh Shah

2020-02-26 08:35:01 +00:00
Commented Feb 26, 2020 at 8:35 — Harsh Shah
– Harsh Shah, Commented Feb 26, 2020 at 8:35

s1m0nw1 · Accepted Answer · 2020-02-26 08:30:08Z

1

You have to call your secondary constructor, which expects a trailing name parameter:

    val person1 = Person("Joe", 25, "name") //prints Age = 25
    val person2 = Person("Joe", 25) //prints nothing

In your example, the primary constructor gets chosen as your argument list maps its parameters.

answered Feb 26, 2020 at 8:30

s1m0nw1

83k17 gold badges181 silver badges201 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

kamal douma · Accepted Answer · 2021-12-19 10:48:51Z

0

in your code val person1 = Person("Joe", 25) your are calling a constructor wich have two parameters and thats the first constructor not the second. call the second constructor like that val person1 = Person("Joe", 25,"name"). i hope that was clear.

answered Dec 19, 2021 at 10:48

kamal douma

5781 gold badge8 silver badges19 bronze badges

Collectives™ on Stack Overflow

How to access primary constructor parameters inside secondary constructor kotlin

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related