How to make multiple constructor generic data Class in kotlin

Question

I want to use multple Constructors like this :

data class MyData<T>(
    val code: String,
    val message: String,
    val data: T? = null,
) {
    constructor(code: String, message: String) : this(code, message, null)
}

and I Use

MyData(code = "-1", message = "Support only application/json Content-Type") // Error :  Not Enough Information To Infer Parameter T
MyData(code = "-1", message = "message", data = "data")

How to Use MyData property 'data' default value is 'null'? ( I want to MyData(code, message) not MyData(code, message) )

Your secondary constructor is redundant. By providing a default value for the third parameter, you’ve already created a second constructor that allows you to omit that parameter. — Tenfour04
– Tenfour04, Commented Feb 12, 2022 at 16:49

lukas.j · Accepted Answer · 2022-02-12 16:34:23Z

1

You pass the type like this:

val obj1 = MyData<String>(code = "-1", message = "Support only application/json Content-Type")

Note that data should probably be a var instead of a val, or you won't be able to change it.

answered Feb 12, 2022 at 16:34

lukas.j

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3 Comments

Tenfour04 Over a year ago

Immutable classes are a valid and often best design practice.

Tenfour04 Over a year ago

You said it should probably be a var like it’s a mistake to make the class immutable.

lukas.j Over a year ago

There is a second part in my sentence saying "or you won't be able to change it". Maybe not the best way to put it, I'll give you that.

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