如何将字符串与静态 &str 匹配？

Question

I am writing a program that does probably a little bit too much with string processing. I moved most of the literal messages to constants; I'm not sure if that is the proper way in Rust, but I'm used to writing that in C.

I figured out that I cannot easily use my static &str inside a match expression. I can use the text itself, but cannot figure out how to do that properly.

I understand it's a compiler issue, but don't know how to write that construction properly in Rust style. Should I use enums instead of C-like static variables?

static SECTION_TEST: &str = "test result:";
static STATUS_TEST_OK: &str = "PASSED";

fn match_out(out: &String) -> bool {
    let s = &out[out.find(SECTION_TEST).unwrap() + SECTION_TEST.len()..];

    match s {
        STATUS_TEST_OK => {
            println!("Yes");
            true
        }
        _ => {
            println!("No");
            false
        }
    }
}

error[E0530]: match bindings cannot shadow statics
 --> src/lib.rs:8:9
  |
2 | static STATUS_TEST_OK: &str = "PASSED";
  | --------------------------------------- the static `STATUS_TEST_OK` is defined here
...
8 |         STATUS_TEST_OK => {
  |         ^^^^^^^^^^^^^^ cannot be named the same as a static

Answer 1

Use a const ant instead of a static:

const STATUS_TEST_OK: &str = "PASSED";

fn match_out(s: &str) -> bool {
    match s {
        STATUS_TEST_OK => {
            println!("Yes");
            true
        }
        _ => {
            println!("No");
            false
        }
    }
}

See also:

• What is the difference between a const variable and a static variable and which should I choose?
• What is the difference between immutable and const variables in Rust?
• How to match a String against string literals in Rust?
• Why is this match pattern unreachable when using non-literal patterns?

Answer 2

For those unable to change the static to a const—although it's a little convoluted—another option is to use an if statement, which will return the &str (or whatever is defined) that lives in the static's NAME:

static STATUS_TEST_OK: &str = "PASSED";

fn match_out(s: &str) -> bool {

    match s {
        str if str == STATUS_TEST_OK => {
            println!("Yes");
            true
        }
        _ => {
            println!("No");
            false
        }
    }
}