Table of Contents📚

• What is a struct method❔
• The impl keyword
• Multiple methods

Struct methods🛠️

What is a struct method❔

Structs methods are functions that are attached to structs, to make them easier to use.

The impl keyword

If we have a struct named Person

struct Person {
    name: String,
    age: u8,
    hobbies: Vec<String>,
    country: String,
    company: String,
}

ℹ️ hobbies is a vector of strings.

We can create a method for the struct that will introduce the person.

To declare methods for a struct, we use the impl keyword, like this:

impl Person {
    fn introduce(&self) {
        println!("Hi, my name is {}, I'm {} years old and I live in {}. I work at {} and my hobbies are: {}", self.name, self.age, self.country, self.company , self.hobbies.join(", "));
    }
}

ℹ️ The function takes the &self parameter, that corresponds to the struct instance that we want to use the method on.

ℹ️ The join method is a method that joins the items of a vector with a separator to create a string.

We can now create a new instance of the struct and use the method.

fn main() {
    let person = Person {
        name: String::from("Léopold"),
        age: 13,
        hobbies: vec![String::from("💻"), String::from("🛌"), String::from("🍔")],
        country: String::from("France 🇫🇷"),
        company: String::from("Skwal-net"),
    };

    person.introduce();
}

ℹ️ The String::from is a function that creates a String from from a str. str and String are different types, but they are both used to represent strings. String have a lot of methods, but str only have a few. By default, in the code "hello", the type is str.

Output:

Hi, my name is Léopold, I'm 13 years old and I live in France 🇫🇷. I work at Skwal-net and my hobbies are: 💻, 🛌, 🍔

Multiple methods

We can also create multiple methods for a struct.

let’s add a method is_adult to the struct Person:

impl Person {
    fn introduce(&self) {
        ...
    }

    fn is_adult(&self) -> bool {
        self.age >= 18
    }
}

ℹ️ the is_adult doesn’t need the return keyword, because when a method returns a value, it returns the value of the last expression.

We can now use the method is_adult on the instance of the struct.

fn main() {
    let person = Person {
       ...
    };

    if person.is_adult() {
        println!("{} is an adult ✅", person.name);
    } else ❔{
        println!("{} is not an adult ⛔", person.name);
    }
}

Output:

Léopold is not an adult ⛔

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