How do I save a string value on Substrate's smart contract platform, ink?

Question

1. I initially tried the implementation as taught in this question. (How can I save string value on Substrate)
2. However, an error occurred in relation to "ink_abi" and the struct could not be defined.
3. Looking at the latest "ink! example"(), I tried to copy it because the struct was defined, but the following command does not work. (https://github.com/paritytech/ink/blob/master/examples/runtime-storage/lib.rs)

cargo +nightly generate-metadata

4. How can I save the string data to the blockchain with "substrate ink!"?
5. I would like to see a sample source if available.

Answer 1

Use ink_prelude::string::String

#![cfg_attr(not(feature = "std"), no_std)]
use ink_lang as ink;

#[ink::contract]
mod foo {
    use ink_prelude::string::String;

    // ...
}

And don't forget to add ink_prelude to your [dependencies] section in your .toml

see: https://paritytech.github.io/ink/ink_prelude/string/struct.String.html