string 如何在 Rust 中将字符串与字符串文字进行匹配？
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How to match a String against string literals in Rust?
提问by Jeroen
I'm trying to figure out how to match a Stringin Rust.
我想弄清楚如何String在 Rust 中匹配 a 。
I initially tried matching like this, but I figured out Rust cannot implicitly cast from std::string::Stringto &str.
我最初尝试这样匹配，但我发现 Rust 不能隐式地从std::string::Stringto 转换&str。
fn main() {
let stringthing = String::from("c");
match stringthing {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
}
}
This has the error:
这有错误：
error[E0308]: mismatched types
--> src/main.rs:4:9
|
4 | "a" => println!("0"),
| ^^^ expected struct `std::string::String`, found reference
|
= note: expected type `std::string::String`
found type `&'static str`
I then tried to construct new Stringobjects, as I could not find a function to cast a Stringto a &str.
然后我尝试构造新String对象，因为我找不到将 aString转换为a 的函数&str。
fn main() {
let stringthing = String::from("c");
match stringthing {
String::from("a") => println!("0"),
String::from("b") => println!("1"),
String::from("c") => println!("2"),
}
}
This gave me the following error 3 times:
这给了我以下错误 3 次：
error[E0164]: `String::from` does not name a tuple variant or a tuple struct
--> src/main.rs:4:9
|
4 | String::from("a") => return 0,
| ^^^^^^^^^^^^^^^^^ not a tuple variant or struct
How to actually match Strings in Rust?
如何String在 Rust 中实际匹配s？
采纳答案by Anonymous Coward
You can do something like this:
你可以这样做：
match &stringthing[..] {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("something else!"),
}
There's also an as_strmethod as of Rust 1.7.0:
as_str从 Rust 1.7.0 开始，还有一个方法：
match stringthing.as_str() {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("something else!"),
}
回答by Tijs Maas
as_sliceis deprecated, you should now use the trait std::convert::AsRefinstead:
as_slice已弃用，您现在应该改用 trait std::convert::AsRef：
match stringthing.as_ref() {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("something else!"),
}
Note that you also have to explicitly handle the catch-all case.
请注意，您还必须明确处理包罗万象的情况。
回答by Marco Scannadinari
You could also do
你也可以这样做
match &stringthing as &str {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("something else!"),
}
See:
看：
回答by A.B.
Editor's note: This answer pertains to an version of Rust before 1.0 and does not work in Rust 1.0
编者注：此答案适用于 1.0 之前的 Rust 版本，不适用于 Rust 1.0
You can match on a string slice.
您可以匹配字符串切片。
match stringthing.as_slice() {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("something else!"),
}
回答by omrihhh
You can try:
你可以试试：
fn main() {
let stringthing = String::from("c");
match &*stringthing {
"a" => println!("0"),
"b" => println!("1"),
"c" => println!("2"),
_ => println!("else")
}
}
