在 Rust 中将字符串转换为 &str [duplicate]

问：

我正在尝试将 a 转换为 .但问题是 rust 总是会抛出这个错误：String&str

error[E0515]: cannot return value referencing local variable `contents`
   --> src/utils.rs:111:5
    |
72  |         let contents = &contents[..];
    |                         -------- `contents` is borrowed here
...
111 |     result
    |     ^^^^^^ returns a value referencing data owned by the current function

For more information about this error, try `rustc --explain E0515`.

如何将变量转换为 &str？