What is the purpose of the `remember` function in Compose?

What's really being asked

This question tests your fundamental understanding of the Compose runtime model. The interviewer isn't just checking for syntax; they are probing your mental model of recomposition. They want to confirm you understand that composables are stateless functions that are re-executed frequently, and that state must be explicitly preserved across these executions. It's a test of whether you've moved beyond thinking in terms of imperative UI toolkits.

The full answer

First, explain that composables are stateless by default and are re-executed (recomposed) whenever their inputs or state they read from changes. Second, describe the problem this creates: any local variable defined inside a composable would be reset to its initial value on every recomposition, losing any changes. Third, introduce remember as the solution. It's a function that stores a value in the Composition's memory (the slot table) during the initial composition and returns that same stored instance during subsequent recompositions. Finally, clarify the relationship with mutableStateOf: mutableStateOf creates an observable state holder, but remember is what ensures you're using the same state holder instance across recompositions.

The mistakes people make

Failing to distinguish remember from rememberSaveable is the most common red flag for a senior candidate. remember only preserves state across recompositions. It does NOT survive configuration changes (like screen rotation) or process death. rememberSaveable handles this by saving the state to the Bundle. Another weak answer is simply stating "it remembers things" without connecting it to the problem of recomposition. A candidate who writes val count = mutableStateOf(0) without remember fundamentally misunderstands how Compose works, as the state would reset on any UI update.

What usually comes next

Expect follow-ups like: "When would you use rememberSaveable instead?" to test the distinction directly. Another is, "What is the purpose of passing a key to remember, as in remember(key1) { ... }?" (Answer: It invalidates and re-executes the lambda when the key changes). A deeper question might be, "How does remember work internally?" (Answer: It stores the calculated value in a data structure called the slot table, associating it with the composable's position in the UI tree).

A concrete example

Here is a simple counter. The state count is created by mutableStateOf(0). The remember block ensures that the MutableState<Int> object itself is preserved across recompositions. Without remember, count would be reset to 0 every time the button was clicked and the Counter composable was recomposed.

@Composable fun Counter() {

var count by remember { mutableStateOf(0) }

Button(onClick = { count++ }) {
Text("Count is $count")
}
}