Structs: Defining Custom Data Types – in Rust

What You’ll Learn 📚

• What structs are and why they’re useful
• How to define and use structs in Rust
• Common pitfalls and how to avoid them
• Practical examples and exercises to solidify your understanding

Introduction to Structs

In Rust, a struct is a custom data type that lets you name and package together multiple related values. Think of it like a blueprint for creating complex data structures. Structs are incredibly useful when you want to group different pieces of data together, like the properties of a car or the attributes of a user in a system.

💡 Lightbulb Moment: If you’ve used classes in other languages, structs in Rust serve a similar purpose but with some differences.

Key Terminology

• Struct: A custom data type that groups together related data.
• Field: A single piece of data within a struct.
• Instance: A specific example of a struct with actual values.

Let’s Start with the Basics

struct Car {
    make: String,
    model: String,
    year: u16,
}

Creating an Instance

fn main() {
    let my_car = Car {
        make: String::from("Toyota"),
        model: String::from("Corolla"),
        year: 2020,
    };
    println!("I drive a {} {} from {}.", my_car.make, my_car.model, my_car.year);
}

Progressively Complex Examples

Example 2: Structs with Methods

impl Car {
    fn display_info(&self) {
        println!("Car: {} {}, Year: {}", self.make, self.model, self.year);
    }
}
fn main() {
    let my_car = Car {
        make: String::from("Toyota"),
        model: String::from("Corolla"),
        year: 2020,
    };
    my_car.display_info();
}

Example 3: Tuple Structs

struct Color(u8, u8, u8);
fn main() {
    let black = Color(0, 0, 0);
    println!("Black color RGB: ({}, {}, {})", black.0, black.1, black.2);
}

Example 4: Structs with Lifetimes

struct Book<'a> {
    title: &'a str,
    author: &'a str,
}
fn main() {
    let book = Book {
        title: "1984",
        author: "George Orwell",
    };
    println!("{} by {}", book.title, book.author);
}

Common Questions and Answers

1. What is a struct in Rust?

   A struct is a custom data type that groups related data together, allowing you to create complex data structures.

2. How do I define a struct?

   Use the struct keyword followed by the struct name and curly braces containing field definitions.

3. Can structs have methods?

   Yes, you can define methods for structs using impl blocks.

4. What’s the difference between a tuple struct and a regular struct?

   Tuple structs don’t have named fields and are accessed by index, while regular structs have named fields.

5. Why use lifetimes with structs?

   Lifetimes ensure that references within structs are valid for the struct’s lifetime, preventing dangling references.

Troubleshooting Common Issues

• Missing Lifetime Specifier: Ensure all references in structs have appropriate lifetime parameters.
• Field Not Found: Double-check field names and ensure they match the struct definition.
• Type Mismatch: Ensure field types match the expected types in the struct definition.

🔗 Additional Resources: Check out the Rust Book for more on structs.

Practice Exercises

• Create a struct to represent a Person with fields for name, age, and email. Add a method to display the person’s info.
• Define a tuple struct for a Point in 2D space and write a function to calculate the distance between two points.

Remember, practice makes perfect! Keep experimenting with structs, and soon you’ll be a Rust struct expert! 🚀