How can I convert char to string?

Question

This question pertains to a pre-release version of Rust. This younger question is similar.

I tried to print one symbol with println:

fn main() {
    println!('c');
}

But I got next error:

$ rustc pdst.rs
pdst.rs:2:16: 2:19 error: mismatched types: expected `&str` but found `char` (expected &str but found char)
pdst.rs:2     println!('c');
                          ^~~
error: aborting due to previous error

How do I convert char to string?

Direct typecast does not work:

let text:str = 'c';
let text:&str = 'c';

It returns:

pdst.rs:7:13: 7:16 error: bare `str` is not a type
pdst.rs:7     let text:str = 'c';
                       ^~~
pdst.rs:7:19: 7:22 error: mismatched types: expected `~str` but found `char` (expected ~str but found char)
pdst.rs:7     let text:str = 'c';
                             ^~~
pdst.rs:8:20: 8:23 error: mismatched types: expected `&str` but found `char` (expected &str but found char)
pdst.rs:8     let text:&str = 'c';
                                  ^~~

score 81 · Accepted Answer · edited Apr 15 '20 at 17:28

81

Use char::to_string, which is from the ToString trait:

fn main() {
    let string = 'c'.to_string();
    // or
    println!("{}", 'c');
}

edited Apr 15 '20 at 17:28

Kornel

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answered Apr 28 '13 at 20:55

Hubro

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Yes, weirdly the docs refer to to_string() but never actually define it. – Josh Hansen Feb 14 '19 at 22:17
2

It's from the `ToString` trait, which is automatically implemented on anything that implements the `Display` trait, which includes `char`. (`impl ToString for T where T: Display + ?Sized`) This indirection, however, means that this won't show up in documentation, and is just something you have to memorize/learn. – Alex Nov 01 '19 at 04:47

score 21 · Answer 2 · edited May 24 '15 at 17:48

21

You can now use c.to_string(), where c is your variable of type char.

edited May 24 '15 at 17:48

Shepmaster

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answered Jan 25 '15 at 12:56

Amandasaurus

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This doesn't seem documented explicitly, but it's true because char's implement Display and Display implementations require to_string, but you wouldn't know that from the Display documentation, this is documented on the ToString trait. Which is not very good. https://doc.rust-lang.org/std/string/trait.ToString.html – Bjorn Feb 09 '17 at 23:41

score 10 · Answer 3 · edited Nov 14 '21 at 02:22

10

Using .to_string() will allocate String on heap. Usually it's not any issue, but if you wish to avoid this and want to get &str slice directly, you may alternatively use

let mut tmp = [0u8; 4];
let your_string = c.encode_utf8(&mut tmp);

edited Nov 14 '21 at 02:22

Evan Shaw

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answered Jun 09 '21 at 05:42

alagris

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How can I convert char to string?

3 Answers3

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