Rust学习笔记

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let s1 = String::from("hello");
let s2 = s1;// s1 的值移动到 s2
            // ... 所以 s2 到这里不再有效
println!("{}, world!", s1); // 此处s1已经没有"hello"的所有权

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error[E0382]: use of moved value: `s1`
 --> src/main.rs:5:28
  |
3 |     let s2 = s1;
  |         -- value moved here
4 |
5 |     println!("{}, world!", s1);
  |                            ^^ value used here after move
  |
  = note: move occurs because `s1` has type `std::string::String`, which does
  not implement the `Copy` trait

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fn main() {
    let s = String::from("hello"); // s 进入作用域
    takes_ownership(s); // s 的值移动到函数里 ...
                        // ... 所以到这里不再有效
    println!("{}", s);
}

fn takes_ownership(x: String) {
    println!("{}", x);
}

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2 |     let s = String::from("hello"); // s 进入作用域
  |         - move occurs because `s` has type `String`, which does not implement the `Copy` trait
3 |     takes_ownership(s); // s 的值移动到函数里 ...
  |                     - value moved here
4 |                         // ... 所以到这里不再有效
5 |     println!("{}", s);
  |                    ^ value borrowed here after move
  |
  = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)

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fn main() {
    let s = String::from("hello"); // s 进入作用域
    takes_ownership(&s); // &s表示在takes_ownership中只读，并不会修改他的值
                        // 所以到这里不再有效
    println!("{}", s);
}

fn takes_ownership(x: &String) {
    println!("{}", x);
}

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fn main() {
   let mut s = String::from("hello");

    let r1 = &s;
    let r2 = &s;
    println!("{} and {}", r1, r2);
    // 新编译器中，r1,r2作用域在这里结束

    let r3 = &mut s;
    println!("{}", r3);
} // 新编译器中，r3作用域在这里结束