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In this lesson, we will talk about Structs in Rust
What are Structs?
Structs are a way to create more complex data types.
They are similar to tuples, but with a few differences.
For example, you can name the fields of a struct (and you can also define methods for structs).
If you prefer a video version
All the code is available on GitHub (link available in the video description)
Define a Struct
Let’s say that we want to crete a User, with name, email, is_active and age. We can define a struct like this:
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
And then you can create an instance of the struct like this:
rust
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
fn main() {
let user = User {
name: String::from(“Jhon Doe”),
email: String::from(“[email protected]“),
is_active: true,
age: 25,
};
}
## Accessing Struct Fields
You can access the fields of a struct using dot notation:
rust
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
fn main() {
let user = User {
name: String::from(“Jhon Doe”),
email: String::from(“[email protected]“),
is_active: true,
age: 25,
};
println!("User name: {}", user.name);
}
Explanaition:
- We define a struct called User with four fields: name, email, is_active and age.
- We create an instance of the struct and assign it to the user variable.
- We access the name field of the user struct using dot notation (user.name).
[](https://youtu.be/PCjuO-Bv5FI)
## Mutable Structs
You can make a struct mutable by using the mut keyword:
rust
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
fn main() {
let mut user = User {
name: String::from(“Jhon Doe”),
email: String::from(“[email protected]“),
is_active: true,
age: 25,
};
user.name = String::from("Francesco");
println!("User name: {}", user.name);
}
[](https://youtu.be/PCjuO-Bv5FI)
Note the you can't make individual fields of a struct mutable, you can only make the entire struct mutable.
## Create a Struct instance using a function
You can create a function that returns a struct instance:
rust
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
fn main() {
let user = create_user(String::from(“Jhon Doe”), String::from(“doe@mail”),);
println!("User name: {}", user.name);
}
fn create_user(name: String, email: String,) -> User {
User {
name,
email,
is_active: true,
age : 25,
}
}
You can see the init shorthand syntax in the create_user function. This is a shorthand for initializing fields with variables that have the same name as the fields.
[](https://youtu.be/PCjuO-Bv5FI)
## Creating Instances from Other Instances with Struct Update Syntax
You can create a new instance of a struct using another instance with the struct update syntax:
rust
struct User {
name: String,
email: String,
is_active: bool,
age: u8,
}
fn main() {
let user1 = User {
name: String::from(“Jhon Doe”),
email: String::from(“[email protected]“),
is_active: false,
age: 40
};
let new_user = User {
name: String::from("Francesco"),
email: user1.email,
is_active: user1.is_active,
age: user1.age,
};
println!("User name: {}", new_user.name);
}
In this example, we create a new instance of the User struct using the user1 instance with the struct update syntax.
[](https://youtu.be/PCjuO-Bv5FI)
## Tuple Structs
Tuple structs are similar to regular structs, but their fields are not named:
rust
struct Color(i32, i32, i32);
struct Point(i32, i32, i32);
fn main() {
let black = Color(0, 0, 0);
let origin = Point(0, 0, 0);
println!(“Black color: {}, {}, {}”, black.0, black.1, black.2);
println!(“Origin: {}, {}, {}”, origin.0, origin.1, origin.2);
}
In this example, we define two tuple structs: Color and Point. We create instances of these tuple structs and access their fields using dot notation.
[](https://youtu.be/PCjuO-Bv5FI)
## Unit-Like Structs
You can define a struct with no fields, called a unit-like struct:
rust
struct User;
fn main() {
let user = User;
println!(“User: {:?}”, user);
}
Unit-like structs are useful when you need to implement a trait on a type but don't have any data to store in the type.
[](https://youtu.be/PCjuO-Bv5FI)
## Conclusion
Structs are a way to create more complex data types in Rust. They are similar to tuples, but with a few differences. You can name the fields of a struct (and you can also define methods for structs). You can also make a struct mutable by using the mut keyword.
You can create a function that returns a struct instance. You can create a new instance of a struct using another instance with the struct update syntax. You can define tuple structs and unit-like structs.
I hope this lesson was useful. In the next lesson, we will see a practical example of using structs in Rust.
If you prefer a video version
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All the code is available on [GitHub](https://youtu.be/PCjuO-Bv5FI) (link available in the video description)
You can find me on https://francescociulla.com and on [Twitter/X](https://twitter.com/FrancescoCiull4)
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