The difference between function and method in rust

In programming languages , In particular, it supports both process oriented style , It also supports object-oriented programming languages , There are usually two nouns, function and method , Used to represent an executable named code block .
Function English is function, Method English is method.
stay Java in , Except for the basic types int、long、double etc. , Everything is the object , Objects have methods .Java There is no function in . Even if lambda The function like things in the expression are just syntax sugar , The method of anonymous object is still used behind . stay Java Methods cannot be passed directly in , The object must be passed .
stay C In language , All of them complete logical processing through functions , Functions don't need to be attached to anyone , It is a first-class citizen , You can pass function pointers around .
stay Rust in , At the same time, there are the concepts of function and method .Rust The functions in and C Similar in language ,Rust Methods and methods in Java Is similar to , It is generally defined in the encapsulated data struct、tuple、enum Above .

For example, the following code can clearly understand the difference between functions and methods ：

fn main() {
    
    let a = 10;
    let b = 40;
    println!("function add result:{}",add(a,b));

    let computer = Computer{
    
        a,
        b,
    };
    println!("method add result:{}",computer.add());
}

//  function  function ( Process oriented style , similar C Functions in language )
fn add(a:i32,b:i32) ->i32{
    
    a+b
}

struct Computer{
    
    a:i32,
    b:i32,
}

impl Computer {
    
    //  Method  method ( Object oriented style , similar Java Object method in )
    pub fn add(&self) ->i32{
    
        self.a+self.b
    }
}