I am confused about secondary constructors Kotlint avoid hav

Question

I am confused about secondary constructors Kotlint avoid having an incomplete object constructed by forcing me to immediatly call the primary constructor But I do not know how I can actually calculate the value for the primary constructor I want to run code to calculate the value that is the whole point of the second constructor I can do it by using a function ```private data class MyClass val intVal Int constructor stringVal String this someFunction stringVal fun someFunction stringVal String Int println I can run some random code here val foo = stringVal reversed return foo toInt ``` But how could I run code on the secondary constructor without using a function

ephemient · Answer

note that Java has the same limitation you cannot run any whole blocks of code before delegating to another constructor only expressions

ephemient · Answer

but in Kotlin expressions are very expressive and include things like `run `

ephemient · Answer

so you could in theory write ```private data class MyClass val intVal Int constructor stringVal String this run println I can run some random code here val foo = stringVal reversed return run foo toInt ```

ephemient · Answer

I thnk it s poor style though

ephemient · Answer

it would be more Kotlin esque to have a constructor like function ```fun MyClass stringVal String MyClass println I can run some random code here val foo = stringVal reversed return MyClass foo toInt ```

Draget · Answer

I see Would this function live inside the class I guess I should treat it like a factory method then

ephemient · Answer

no outside

ephemient · Answer

there is an alternative placement ```class MyClass private constructor companion object operator fun invoke MyClass arbitrary logic here return MyClass ``` but I d only use it in cases where the function outside doesn t work due to visibility

Draget · Answer

Funny I never realized this issue in Java because it is common to have a constructor that copies the values to an internal variable Doing it like this allows multiple constructors initializing the Instance In Kotlin it is made just way more visible that in this case I have an uninitalized object in that moment I guess I could do this in Kotlin ```private data class MyClass var intVal Int constructor stringVal String this 0 this intVal = stringVal toInt ```

Draget · Answer

But why would you conside a factory like Method inside the class bad style ```private data class MyClass var intVal Int companion object fun ofString stringVal String MyClass = MyClass stringVal toInt ```

ephemient · Answer

that s fine although depending on the use case it may be more natural as an extension function ```fun String toMyClass MyClass```

Draget · Answer

In cases where I need this as a kind of helper in my current class I usually use extension functions But if I want the ability to be created from a String to be something of my class it should be part of said class at least that is what I would consider proper separation of concerns

Draget · Answer

Thanks for the input slightly smiling face I think I got a better feel for it now