compose-slot-api-pattern

What problem does it solve?

It prevents reusable Jetpack Compose components from becoming hard to extend when visual content differs across call sites and parameters start turning into an ever-growing list of primitives and booleans.

Core Features & Use Cases

• Replace primitive content params with composable slots: delegate variable UI regions to caller-provided @Composable lambdas so the component defines structure while the caller defines content.
• Use scope receivers when the slot needs layout APIs: declare slots as @Composable RowScope.() -> Unit (or BoxScope/ColumnScope) when the slot is rendered inside that layout so callers can use weight, alignment, and scope-specific modifiers.
• Model optional UI as nullable slots: prefer (@Composable () -> Unit)? = null over empty-lambda defaults to clearly distinguish “absent” from “present but empty,” enabling the component to skip spacing and containers.
• Centralize common defaults in XxxDefaults: move reusable default slot content into a nearby Defaults object so the main component API stays clean and call sites remain concise.
• Use-case example: when designing a reusable settings/list row that might show an icon, a badge, a switch, or custom trailing content depending on the screen, slot the leading/headline/supporting/trailing regions instead of enumerating variants and flags.

Quick Start

Refactor your reusable Compose component so every caller-controlled visual region is exposed as a dedicated @Composable slot, using nullable slots for optional regions and a scope receiver only when the slot’s layout context needs it.