How to stop Kotlin flow when certain condition occurs

Question

I want to cancel kotlin flow if certain condition occurred in code.

Suppose i have a method as following

fun test(): Flow<String> = flow {
    val lst = listOf("A", "B", "C")

    while(true) {
        lst.forEach { emit(it) }

    //If some condition occurs, need to return from here, else continue
    //How to stop flow here
    }
}

and calling it like

test().collect { println(it)}

question is, how to stop flow to produce anything on certain conditions (from flow builder or outside of it)?

Answer 1

fun test(): Flow<String> = flow {
    val lst = listOf("A", "B", "C")

    while(true) {
        lst.forEach { emit(it) }

        if (someCondition) {
            return@flow
        }
    }
}

return@flow instantly returns from flow lambda, so the flow will be ended. As another option, you can just break your while(true) loop when your condition occurs.