maybe this ll end up being a dumb question but what s the ri

Question

maybe this ll end up being a dumb question but what s the right approach to take when you have a property you want to assign conditionally based on which constructor you call the class I m writing kinda looks like this ``` class Foo val bar val baz val doober = mutableMapOf lt String String gt val qux Set lt String gt constructor bar baz lad this bar baz do things to `doober` using `lad` qux = doober keys toSet ``` more specifically `qux` should be an empty set if the primary constructor is called and a computed read only set if the secondary constructor is called based on the results of evaluating the parameter unique to it I tried a separate `init` block declared after the secondary constructor to populate the set using the map but it looks like the init block gets executed before the logic in the body of the secondary constructor for kicks I also tried making `qux` a constructor parameter but you can t call the primary constructor from the secondary one using values you compute in the latter

edwardwongtl · Answer

Note that code in initializer blocks effectively becomes part of the primary constructor Delegation to the primary constructor happens as the first statement of a secondary constructor so the code in all initializer blocks is executed before the secondary constructor body Even if the class has no primary constructor the delegation still happens implicitly and the initializer blocks are still executed Quoted from official website

Shawn · Answer

gotcha

edwardwongtl · Answer

``` class Foo val doober = mutableMapOf lt String String gt val qux Set lt String gt constructor bar String baz String qux = emptySet constructor bar String baz String lad String do things to `doober` using `lad` qux = doober keys toSet ``` This could work

edwardwongtl · Answer

By making the first `constructor` a non primary one they can both initialize `qux` inside the constructor

Shawn · Answer

what if `bar` and `baz` are `private val`s

edwardwongtl · Answer

``` class Foo private val bar String private val baz String val doober = mutableMapOf lt String String gt val qux Set lt String gt constructor bar String baz String qux = emptySet this bar = bar this baz = baz constructor bar String baz String lad String do things to `doober` using `lad` qux = doober keys toSet this bar = bar this baz = baz ```

Shawn · Answer

is that not the same code

edwardwongtl · Answer

I pressed enter too early

Shawn · Answer

ah gotcha

Shawn · Answer

kind of irritating that you have to assign bar and baz twice though

edwardwongtl · Answer

True but they are in different constructor so

edwardwongtl · Answer

Kind of a trade off atm

edwardwongtl · Answer

Maybe you can file a issue on this and see if JetBrain will take into account

Shawn · Answer

so after spending way too much time trying to resolve this neatly I settled on making that last parameter nullable with null as the default parameter which gets rid of the secondary constructor and uses a ` let ` to do an assignment

Shawn · Answer

it looks not amazing but it s not the literal worst

Shawn · Answer

I also don t know if it s a code smell to have a nullable param that defaults to null

edwardwongtl · Answer

definitely not