`val fullTariffList = arrayOf("customer", "reselle...

# announcements

[cy]

val fullTariffList = arrayOf("customer", "reseller", "vendor").flatMap { type -> testTariffList.map { it.copy(type = type) } }

[mike_shysh]

Thanks, your solution is perfect) But I also want to understand what is going on in my example)

[mike_shysh]

Why fullTariffList.add(tariffInfo) is always contains vendor. I think I am missing some knowledge about forEach

[r4zzz4k]

You are basically adding one item three times into the list.

[mike_shysh]

but println(tariffInfo); shows me that tariffInfo is different in every iteration

[mike_shysh]

fullTariffList.add(tariffInfo) processed after finishing forEach?

[mike_shysh]

May be someone could point me to docs)

[r4zzz4k]

class Object { var type: String }

val list = mutableListOf<Object>()
val obj = Object()

obj.type = "1"
println(obj.type) // "1"
list += obj // list has one reference to obj, it's type is "1"

obj.type = "2"
println(obj.type) // "2"
list += obj // list has two reference to the same obj, it's type is "2"

obj.type = "3"
println(obj.type) // "3"
list += obj // list has three reference to the same obj, it's type is "3"

list.forEach {
    println(it.type)
}
// prints "3 3 3", as it's the same object and last value of type was "3"

[r4zzz4k]

Does it make this clearer?
If you are coming from the language with pointers: your container holds objects by reference, not by value. So .copy allows you to create new object every iteration and list would have different objects inside it.

[mike_shysh]

Yeah, I got your example

[mike_shysh]

Thank you

[nkiesel]

that flatMap solution creates a list with the same items but in a different order than the original code. Turning it inside out would fix this:

testTariffList.flatMap { item -> arrayOf("customer", "reseller", "vendor").map { item.copy(type = it) } }

[mike_shysh]

in general, order does not matter. Neverthless it's useful example, thanks