Rust for C-Programmers

9.1 Introduction to Structs and Comparison with C

In Rust, structs allow developers to define custom data types composed of several related values, called fields. While similar to C’s struct, Rust introduces important distinctions and variations.

The most common form is a struct with named fields:

Rust:

struct Person {
    name: String,
    age: u8,
}

C:

struct Person {
    char* name; // Often a pointer, manual memory management needed
    uint8_t age;
};

Key differences and enhancements in Rust include:

1. Memory Safety: Rust’s ownership and borrowing rules guarantee memory safety at compile time, preventing issues like use-after-free or data races that can occur with C structs containing pointers. Fields like String manage their own memory.
2. Methods and Behavior: Rust structs can have associated functions and methods defined in separate impl blocks. This bundles data and behavior logically, unlike C where functions operating on structs are defined globally or rely on function pointers.
3. Struct Variants: While named-field structs are common, Rust also offers tuple structs (with unnamed fields accessed by index) and unit-like structs (with no fields at all). These variants serve specific purposes, discussed later.
4. No Inheritance: Unlike classes in C++, Rust structs do not support implementation inheritance. Code reuse and polymorphism are achieved through traits and composition.

Rust structs combine the data aggregation capabilities of C structs with enhanced safety, associated behavior, and different structural variants, forming a powerful tool for building complex data structures.