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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

#![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

#![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

#![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

#![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

#![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

#![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

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 errorFor 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