Rust struct
- 1.实例化需要初始化全部成员变量
- 2.如果需要实例化对象可变，加上mut则所有成员变量均可变
Rust支持通过已实例化的对象，赋值给未赋值的对象的成员变量
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
fn main() -> Result<(), Box<dyn Error>> {
let u: User = User {
name: String::from("sqs"),
age: 12
};
print!("{} {} ", u.name, u.age);
let b: User = User {
name: String::from("sqssqs"),
..u
};
print!("{} {}", b.name, b.age);
Ok(())
}定义结构体中的方法
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
impl User {
fn print(&self) {
println!("{} {}", self.name, self.age);
}
}
fn main() -> Result<(), Box<dyn Error>> {
let u: User = User {
name: String::from("sqs"),
age: 12
};
u.print();
let b: User = User {
name: String::from("sqssqs"),
..u
};
b.print();
Ok(())
}修改成员变量
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
fn main() -> Result<(), Box<dyn Error>> {
let mut u: User = User {
name: String::from("sqs"),
age: 12
};
print!("{} {} ", u.name, u.age);
u.name = String::from("sqssqs");
u.age = 16;
print!("{} {}", u.name, u.age);
Ok(())
}通过 借用 修改成员变量
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
fn chageAge(u : &mut User){
u.age = 10;
}
fn main() -> Result<(), Box<dyn Error>> {
let mut u: User = User {
name: String::from("sqs"),
age: 12
};
println!("{} {}", u.name, u.age);
u.name = String::from("sqssqs");
u.age = 16;
println!("{} {}", u.name, u.age);
chageAge(&mut u);
println!("{} {}", u.name, u.age);
Ok(())
}通过 转移所有权 修改成员变量
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
fn chageAge(mut u: User) -> User {
u.age = 10;
u
}
fn main() -> Result<(), Box<dyn Error>> {
let mut u: User = User {
name: String::from("sqs"),
age: 12
};
println!("{} {}", u.name, u.age);
u.name = String::from("sqssqs");
u.age = 16;
println!("{} {}", u.name, u.age);
u = chageAge(u);
println!("{} {}", u.name, u.age);
Ok(())
}以下代码报错
rust
#![allow(warnings)]
use std::io;
use std::error::Error;
use std::boxed::Box;
use std::convert::TryInto;
use std::cmp::Ordering;
use std::cmp::min;
use std::cmp::max;
struct User {
name: String,
age: i32
}
fn chageAge(mut u: User) -> User {
u.age = 10;
u
}
fn main() -> Result<(), Box<dyn Error>> {
let mut u: User = User {
name: String::from("sqs"),
age: 12
};
println!("{} {}", u.name, u.age);
u.name = String::from("sqssqs");
u.age = 16;
println!("{} {}", u.name, u.age);
let b: User = chageAge(u);
println!("{} {}", u.name, u.age);
Ok(())
}报错详情
rust
编译出错！
error[E0382]: borrow of moved value: `u.age`
--> /main.rs:30:31
|
21 | let mut u: User = User {
| ----- move occurs because `u` has type `User`, which does not implement the `Copy` trait
...
29 | let b: User = chageAge(u);
| - value moved here
30 | println!("{} {}", u.name, u.age);
| ^^^^^ value borrowed here after move
|
= note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
error: aborting due to previous error
For more information about this error, try `rustc --explain E0382`.原因
所有权已经从u给b导致u无法使用