Mapping throws error when trying to use custom struct INK 4.0 beta

Question

I'm trying to use a custom struct inside a Mapping, but I get many errors when trying to compile my code.

Here is the custom struct I want to use inside a Mapping:

#[ink::storage_item]
pub struct Transaction {

        creator:AccountId,
        approvers: Mapping<AccountId, Balance>,
        number_of_approvals:Balance,
        psp22_token_to_transfer:AccountId,
        recipient:AccountId,
        transaction_number:Balance

}

And this is how I try to use the Mapping inside the contract struct:

#[ink(storage)]
pub struct MultiSig {
        
        deployer: AccountId,
        wallet_participants: Vec<AccountId>,
        number_of_participants: Balance,
        number_of_transactions: Balance,
        wallet_tokens: Mapping<AccountId,Balance>,
        wallet_transactions: Mapping<Balance,(Transaction,Balance)>

}

The errors that I get are related to decode and encode and "StorableHint", here are some of the errors that I'm getting:

the trait `parity_scale_codec::Decode` is not implemented for `(multi_sig::Transaction, u128)`


the trait `Encode` is not implemented for `(multi_sig::Transaction, u128)`

the trait `StorableHint<()>` is not implemented for `ink::storage::Mapping<u128, (multi_sig::Transaction, u128)>`

I'm using the following documentation in order to implement a custom struct:

Thank you in advance :)

Answer 1

Update your custom struct like this.

#[derive(scale::Decode, scale::Encode)]
#[cfg_attr(feature = "std",derive(scale_info::TypeInfo, 
 ink::storage::traits::StorageLayout))]

 pub struct Transaction {
        creator:AccountId,
        approvers: Mapping<AccountId, Balance>,
        number_of_approvals:Balance,
        psp22_token_to_transfer:AccountId,
        recipient:AccountId,
        transaction_number:Balance
    }