String conversions in Rust

Sources: 1 and 2

let s: String = ...
let st: &str = ...
let u: &[u8] = ...
let b: [u8; 3] = b"foo"
let v: Vec<u8> = ...
let os: OsString = ...
let ost: OsStr = ...

From	To	Use	Comment
`&str`	`String`	`String::from(st)`
`&str`	`&[u8]`	`st.as_bytes()`
`&str`	`Vec<u8>`	`st.as_bytes().to_owned()`	via `&[u8]`
`&str`	`&OsStr`	`OsStr::new(st)`
`String`	`&str`	`&s`	or `s.as_str()`
`String`	`&[u8]`	`s.as_bytes()`
`String`	`Vec<u8>`	`s.into_bytes()`
`String`	`OsString`	`OsString::from(s)`
`&[u8]`	`&str`	`str::from_utf8(u).unwrap()`
`&[u8]`	`String`	`String::from_utf8(u).unwrap()`
`&[u8]`	`Vec<u8>`	`u.to_owned()`
`&[u8]`	`&OsStr`	`OsStr::from_bytes(u)`	`use std::os::unix::ffi::OsStrExt;`
`[u8; 3]`	`&[u8]`	`&b[..]`	byte literal
`[u8; 3]`	`&[u8]`	`"foo".as_bytes()`	alternative via UTF-8 literal
`Vec<u8>`	`&str`	`str::from_utf8(&v).unwrap()`	via &`[u8]`
`Vec<u8>`	`String`	`String::from_utf8(v)`
`Vec<u8>`	`&[u8]`	`&v`
`Vec<u8>`	`OsString`	`OsString::from_vec(v)`	`use std::os::unix::ffi::OsStringExt;`
`&OsStr`	`&str`	`ost.to_str().unwrap()`
`&OsStr`	`String`	`ost.to_os_string().into_string().unwrap()`	via `OsString`
`&OsStr`	`Cow<str>`	`ost.to_string_lossy()`	Unicode replacement characters
`&OsStr`	`OsString`	`ost.to_os_string()`
`&OsStr`	`&[u8]`	`ost.as_bytes()`	`use std::os::unix::ffi::OsStringExt;`
`OsString`	`String`	`os.into_string().unwrap()`	returns original `OsString` on failure
`OsString`	`&str`	`os.to_str().unwrap()`
`OsString`	`&OsStr`	`os.as_os_str()`
`OsString`	`Vec<u8>`	`os.into_vec()`	`use std::os::unix::ffi::OsStringExt;`

Update: 2023-05-18

See String conversions in Rust follow-up to find out about conversions to/from Path and PathBuf.

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