In Rust, methods and functions are declared using the fn keyword. Here's an example of how to declare a basic function that returns an integer:
fn add_numbers(a: i32, b: i32) -> i32 {
return a + b;
}
This function is named add_numbers and takes two arguments, both of which are i32 integers. The function returns the sum of the two integers which is also an i32.
Here's an example of how to declare a method in Rust:
struct Rectangle {
width: u32,
height: u32,
}
impl Rectangle {
fn area(&self) -> u32 {
return self.width * self.height;
}
}
This method called area is defined within the impl block of the Rectangle struct. It takes a reference to self as an argument and calculates the area of the rectangle using its width and height fields. The method returns the area as a u32.
Note that Rust conventionally uses the snake_case naming convention for functions and methods. The arguments and return types of a function or a method must be declared in the function signature with the correct type. Finally, the return keyword is optional as Rust functions or methods can implicitly return the last expression in them.