我正在尝试执行以下操作
// Just removes redundant white space while also splitting the string
// with a whitespace.
fn split_whitespace(string: &str) -> Vec<&str> {
let words: Vec<&str> = string
.split_whitespace()
.filter(|&word| word != "")
.collect();
words
}
pub fn get_websites_from_hosts(hosts_path: &Path) -> Result<Vec<Website>, std::io::Error> {
let hosts_string = read_to_string(hosts_path)?;
let result: Vec<Website> = hosts_string
.lines()
.filter(|&line| split_whitespace(&line.to_owned()).len() == 2)
.map(|line| {
let ip_domain = split_whitespace(&line.to_owned());
Website {
domain_name: ip_domain[1], // This won't work because it is refering hosts_string which is a local variable of the function
redirect_ip: ip_domain[0], // the same case with this one.
is_blocked: true,
hosts_path,
}
})
.collect();
Ok(result)
}
我想要实现的是成功地返回Website结构体,同时可能不编辑结构体声明。
这是Website结构声明
# [derive(Debug, Clone)]
pub struct Website<'a> {
pub domain_name: &'a str,
pub redirect_ip: &'a str,
pub is_blocked: bool,
pub hosts_path: &'a Path,
}
这就是错误
error[E0515]: cannot return value referencing temporary value
--> src/parser.rs:21:13
|
20 | let ip_domain = split_whitespace(&line.to_owned());
| --------------- temporary value created here
21 | / Website {
22 | | domain_name: ip_domain[1],
23 | | redirect_ip: ip_domain[0],
24 | | is_blocked: true,
25 | | hosts_path,
26 | | }
| |_____________^ returns a value referencing data owned by the current function
For more information about this error, try `rustc --explain E0515`.
error: could not compile `website-blocker` due to previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `website-blocker` due to previous error
我想要一个深刻的解释和一般的提示,以使用时,遇到这个和类似的问题
1条答案
按热度按时间hc2pp10m1#
结构体中的
&str
引用引用了read_to_string
返回的字符串的段。该字符串(hosts_string
)在fn get_websites_from_hosts
的末尾被丢弃和释放,因此如果你可以返回对它的引用,它们将是悬空的。Rust阻止你这样做。相反,您需要将
read_to_string
移出该函数,并将字符串作为&str
传入,或者更改您的结构以保存String
、IpAddr
等拥有的值。如果要避免某些
String
分配,可以使用“小字符串优化”库,如compact_str