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用带有两个字符串字段的struct解释Rust所有权概念
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用带有两个字符串字段的struct解释Rust所有权概念
下面代码struct有两个字符串字段：
#[derive(Debug)]
struct Person {
name: String,
alias: String,
}
fn main() {
let person = Person {
name: "John".to_string(),
alias: "Johan".to_string(),
};
print_alias(person.alias);
println!("{:?}", person);
}
fn print_alias(alias: String) {
println!("Person: {:?}!", alias);
}
|
编译器报错：
error[E0382]: borrow of partially moved value: `person`
--> src/main.rs:12:22
然而，在这个列表中，我们在print_alias之后添加了一个print语句。
这个程序没有被编译，因为person.alias已经部分进入print_alias，但是我们试图在println！行中将person作为一个整体借用。
事实证明，我们可以部分移动字段--只要确保我们以后不要再尝试使用结构本身。
在这里，我们将两个字段移到两个不同的函数中。
#[derive(Debug)]
struct Person {
name: String,
alias: String,
}
fn main() {
let person = Person {
name: "John".to_string(),
alias: "Johan".to_string(),
};
print_alias(person.alias);
print_name(person.name);
}
fn print_alias(alias: String) {
println!("Alias: {:?}!", alias);
}
fn print_name(name: String) {
println!("Name: {:?}!", name);
}
|
输出：
Alias: "Johan"! Name: "John"! |
我们也可以通过引用来传递这些字段。
#[derive(Debug)]
struct Person {
name: String,
alias: String,
}
fn main() {
let person = Person {
name: "John".to_string(),
alias: "Johan".to_string(),
};
print_alias(&person.alias);
print_name(&person.name);
}
fn print_alias(alias: &str) {
println!("Alias: {:?}!", alias);
}
fn print_name(name: &str) {
println!("Name: {:?}!", name);
}
|
或者如果我们以后想再次使用person，我们可以克隆这些值：
#[derive(Debug)]
struct Person {
name: String,
alias: String,
}
fn main() {
let person = Person {
name: "John".to_string(),
alias: "Johan".to_string(),
};
print_alias(person.alias.clone());
print_name(person.name.clone());
println!("{:?}", person);
}
fn print_alias(alias: String) {
println!("Alias: {:?}!", alias);
}
fn print_name(name: String) {
println!("Name: {:?}!", name);
}
|
或者你可以在不需要克隆的情况下移动东西。在这里，我们首先借用了Person，然后部分移动字段。
#[derive(Debug)]
struct Person {
name: String,
alias: String,
}
fn main() {
let person = Person {
name: "John".to_string(),
alias: "Johan".to_string(),
};
println!("{:?}", person);
print_alias(person.alias);
print_name(person.name);
}
fn print_alias(alias: String) {
println!("Alias: {:?}!", alias);
}
fn print_name(name: String) {
println!("Name: {:?}!", name);
}
|
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