如何在 Rust 中执行已实现的方法？

Question

I can't execute method which name is two_sum implemented in a Solution impl.
I want to know how to execute two_sum method from main .

My source code is here.

impl Solution {
    pub fn two_sum(num: i32) -> i32 {
        num + 1
    }
}

fn main() {
    let result = Solution::two_sum(1);
    println!("{:?}", result);
}

Error message

failed to resolve: use of undeclared type Solution
use of undeclared type Solution

Answer 1

You need define what Solution is and later implement two_sum. One way is you can define Solution as an empty struct.

struct Solution;

impl Solution {
    pub fn two_sum(num: i32) -> i32 {
        num + 1
    }
}

fn main() {
    let result = Solution::two_sum(1);
    println!("{:?}", result);
}

Answer 2

Well, firstly, your two_sum is an associated function, not a method. Secondly, it's associated with nothing - you didn't declare a type named Solution (you needed to write struct Solution; at least). Thirdly, you don't need to Debug an i32 , so we'll replace {:?} with {} .

struct Solution;

impl Solution {
    pub fn two_sum(num: i32) -> i32 {
        num + 1
    }
}

fn main() {
    let result = Solution::two_sum(1);
    println!("{}", result);
}

Fourthly, creating a type just to write a function is a really bad practice.

So what are we gonna do?

fn two_sum(num: i32) -> i32 {
    num + 1
}

fn main() {
    let result = two_sum(1);
    println!("{}", result);
}

That's it! I don't know why did you call it two_sum tho.