Chapter 12: Understanding Closures in Rust

Closures in Rust are anonymous functions that can capture variables from the scope in which they are defined. This feature simplifies passing around small pieces of functionality without resorting to function pointers and boilerplate code, as one might do in C. From iterator transformations to callbacks in concurrent code, closures help make Rust code more concise, expressive, and robust.

In C, simulating similar behavior requires function pointers plus a manually managed context (often passed as a void*). Rust closures eliminate that manual overhead and provide stronger type guarantees. This chapter explores how closures interact with Rust’s ownership rules, how their traits (Fn, FnMut, FnOnce) map to different kinds of captures, and how closures can be used in both common and advanced use cases.