Use `lateinit var` for a non‑nullable property that will be initialized later (e.g., in DI or lifecycle), when `null` is not a valid state. It works only for mutable, non‑primitive types. You can check initialization with `::prop.isInitialized`.
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.
Examples
A tiny example (an explanation template):
// Example: discuss trade-offs for "`lateinit`-vs-nullable-property:-when-would-you-"
function explain() {
// Start from the core idea:
// Use `lateinit var` for a non‑nullable property that will be initialized later (e.g., in DI
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).