Structs

3.1. Structs#

Link to Rust documentation for Struc & Impl

A struct, or structure, is a data type in Rust that is composed of data items of different types, including other structures. A structure defines its data as a key-value pair.

3.1.1. Declaring and Instantiating a struct#

To declare a structure, we use the keyword struct followed by the name of the structure. Then, inside the curly brackets, we define the names and types of the pieces of data. For example:

struct name_of_struct {
    field1: data_type,
    field2: data_type,
    field3: data_type
}

After declaring a struct, we create an instance of that struct and specify concrete values for the fields and values. For example:

// declaring an employee structure
struct Employee {
    name: String,
    company: String, 
    age: u32,
    active: Boolean
}
//creating an instance of the struct
fn main() {
    let emp1 = Employee {
        name: String::from("Some Name"),
        company: String::from("Some Company"),
        age: 27,
        active: True
    };
}

In an instance, we define the key: value pairs, where the keys are the names of the fields and the values are the data we want to store in those fields.

There is a common shorthand notation when initializing a struct that you can pass a variable with the same name as the member of the struct.

let age = 27;
let active = true;
let emp1 = Employee {
        name: String::from("Some Name"),
        company: String::from("Some Company"),
        age,
        active
    };

To get a specified value from a struct, we can use dot notation. For example, if we wanted the employee’s name, we would call emp1.name whenever we wanted to use this value.

To be able to modify an instance, the instance variable must be marked as mutable. A reminder on how to make your variables mutable is by adding mut in front of the variable name. If we want to modify a specific key: value pair, we would again use dot notation. For example, if we wanted to modify the company name of emp1, we would call:

emp1.company = String::from("Different Company");

after making the appropriate value mutable.

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