I've got a class that has a constructor with a sin...

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[Martin Barth]

I've got a class that has a constructor with a single parameter and I want to add a couple of different "public" read only members to the class as well. there is a expensive algorithm to calculate the values of each of the members based on the constuctur parameters. How can I run the algorithm only once and populate vals?

[diesieben07]

class MyClass(param1: String, param2: String) {
    val value1: ComputedThingy
    val value2: OtherComputedThingy
    
    init {
        value1 = TODO("heavy computation")
        value2 = TODO("more computation")
    }

[Martin Barth]

ahh cool 🙂

[christophsturm]

why not

class MyClass(param1: String, param2: String) {
    val value1 = TODO("heavy computation")
    val value2= TODO("more computation")

[diesieben07]

I assumed there is some commonality to the computation, which should not be done for each property

[diesieben07]

If that is not the case, do what Christoph said, yes

[Martin Barth]

yeah but that is the case

[Nir]

Yeah, this "commonality" case makes init blocks so nice. I miss this feature in C++ quite a bit on occasion.

[christophsturm]

it would be cool if variables from the init block would be available in the body then you could do

class MyClass(param1: String, param2: String) {
init {val heavy=heavy()}
    val value1 = heavy.one
    val value2= heavy.other

i sometimes do

class MyClass(param1: String, param2: String) {
private val heavy=heavy()
    val value1 = heavy.one
    val value2= heavy.other

[christophsturm]

or if its more complex:

class MyClass(param1: String, param2: String) {
private val heavy= run {
...
heavy() } 
    val value1 = heavy.one
    val value2= heavy.other

[Martin Barth]

what is the benefit of doing that, compared to

val value1
val value2

init {
   value1 = ...
   ....
   value2 = ...
}

[christophsturm]

not having to specify the type

[Martin Barth]

ah!

[Martin Barth]

correct, my example did miss that part!

[Nir]

that's an interesting point christoph