How can I implement BorshDeserialize on struct with a string?

Question

When trying to build by Solana Program, I'm getting this error. Can anybody please tell me how can I serialize String, As I'm using String in my struct. OR instead of String what I should I use if serializing string isn't possible in Solana program?

Struct: Box

#[derive(Clone, Debug, BorshSerialize, BorshDeserialize, PartialEq)]
pub struct Box {
    pub token_uris: [String; 3], 
    pub count: i32,
    pub title: String,
    pub description: String,
    pub image: String,
    pub price: i32,
    pub usd_price: i32,
    pub count_nft: i32,
    pub is_opened: bool,
}

Error Log:

15 | #[derive(Clone, Debug, BorshSerialize, BorshDeserialize, PartialEq)]
   |                                        ^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `std::string::String`
   |
   = note: required because of the requirements on the impl of `AnchorDeserialize` for `[std::string::String; 3]`
   = help: see issue #48214
   = note: this error originates in the derive macro `BorshDeserialize` (in Nightly builds, run with -Z macro-backtrace for more info)

Answer 1

Can anybody please tell me how can I serialize String, As I'm using String in my struct.

The problem is not that you're using a string, or a string in a struct, it's that you're using a string in a fixed-size array, hence the compiler pointing to that specifically:

for `[std::string::String; 3]`

not

for `String`

And if you go read the documentation for BorshDeserialize you can find:

impl<T> BorshDeserialize for [T; 3] where
    T: BorshDeserialize + Default + Copy, 

So BorshDeserialize is only implemented for arrays Default + Copy types. Since a String is not Copy the automatic derivation can not work.

The fixes are to either:

• not use a fixed-size array
• or implement BorshDeserialize by hand on your structure instead of trying to derive() it