Struct data type in Rust

Struct is a custom data type to us group multiple related values together. Sounds like array or tuple, doesn’t it? let’s see how struck is different.

• It can contains multiple data type values (like tuples).
• We assign a name for each of the value as key.

So we won’t rely on the order(index) of the values. Rather, we reference it by it’s key.

How to define a struct

Example struct named user, with multiple values

struct User {
    username: String,
    email: String,
    sign_in_count: u64,
    active: bool,
}

We write key : data type, inside bracket of the struct

How to use struct

After defining it, now we can create an instance of that struct, with filled value on the right side of the key name.

let user1 = User {
    email: String::from("someone@example.com"),
    username: String::from("someusername123"),
    active: true,
    sign_in_count: 1,
};

How to fill specific value in Struct

To fill a specific value, we use the object name (dot) key

let mut user1 = User {
    email: String::from("someone@example.com"),
    username: String::from("someusername123"),
    active: true,
    sign_in_count: 1,
};

user1.email = String::from("anotheremail@example.com");

The variable must be mutable, to be able to change it’s value.

Assign struct dynamically

To make our struct dynamic, we can create a function that return that struct with parameters that we need

struct User {
    username: String,
    email: String,
    sign_in_count: u64,
    active: bool,
}

fn build_user(email: String, username: String) -> User {
    User {
        email: email,
        username: username,
        active: true,
        sign_in_count: 1,
    }
}

fn main() {
    let user1 = build_user(
        String::from("someone@example.com"),
        String::from("someusername123"),
    );
}

if the key and value name is the same, we can write it shortly like this

User {
        email, //no : email needed
        username, //no : username needed
        active: true,
        sign_in_count: 1,
    }