Error on custom rpc in new version

Question

Updating to new version of substrate, of the branch = "polkadot-v0.9.42", it giving error,

impl<C, Block, AccountId> ProfileValidationApi<<Block as BlockT>::Hash, AccountId> for ProfileValidation<C, Block>
where
    Block: BlockT,
    AccountId: Codec,
    C: Send + Sync + 'static,
    C: ProvideRuntimeApi<Block>,
    C: HeaderBackend<Block>,
    C::Api: ProfileValidationRuntimeApi<Block, AccountId>,
{
    fn get_challengers_evidence(
        &self,
        profile_user_account: AccountId,
        offset: u64,
        limit: u16,
        at: Option<<Block as BlockT>::Hash>,
    ) -> Result<Vec<ChallengePostId>> {
        let api = self.client.runtime_api();
        let at = BlockId::hash(at.unwrap_or_else(||
            // If the block hash is not supplied assume the best block.
            self.client.info().best_hash));

        let runtime_api_result =
            api.get_challengers_evidence(&at, profile_user_account, offset, limit);
        runtime_api_result.map_err(|e| RpcError {
            code: ErrorCode::ServerError(9876), // No real reason for this value
            message: "Something wrong".into(),
            data: Some(format!("{:?}", e).into()),
        })
    }

The error:

error[E0308]: mismatched types
   --> pallets/profile-validation/profile-validation-rpc/src/lib.rs:90:33
    |
90  |             api.get_challengers_evidence(&at, profile_user_account, offset, limit);
    |                 ------------------------ ^^^ expected associated type, found `&BlockId<_>`
    |                 |
    |                 arguments to this method are incorrect
    |                 here the type of `api` is inferred to be `<C as ProvideRuntimeApi<Block>>::Api`
    |
    = note: expected associated type `<Block as sp_api::BlockT>::Hash`
                     found reference `&BlockId<_>`
help: a method is available that returns `<Block as sp_api::BlockT>::Hash`
   --> /home/amiya/.cargo/git/checkouts/substrate-7e08433d4c370a21/ff24c60/primitives/runtime/src/traits.rs:951:2
    |
951 |     fn hash(&self) -> Self::Hash {
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ consider calling `sp_api::BlockT::hash`
note: method defined here
   --> /home/amiya/Documents/workspace/shivarthu/working_directory/substrate-node-template/pallets/profile-validation/profile-validation-runtime-api/src/lib.rs:11:6
    |
11  |         fn get_challengers_evidence(profile_user_account: AccountId, offset: u64, limit: u16) -> Vec<ChallengePostId>;
    |            ^^^^^^^^^^^^^^^^^^^^^^^^

Answer 1

New example code is present in transaction-payment rpc that uses jsonrpsee

https://github.com/paritytech/substrate/blob/master/frame/transaction-payment/rpc/src/lib.rs

impl<C, Block, AccountId> ProfileValidationApiServer<<Block as BlockT>::Hash, AccountId> for ProfileValidation<C, Block>
where
    Block: BlockT,
    AccountId: Codec,
    C: Send + Sync + 'static,
    C: ProvideRuntimeApi<Block>,
    C: HeaderBackend<Block>,
    C::Api: ProfileValidationRuntimeApi<Block, AccountId>,
{
    fn get_challengers_evidence(
        &self,
        profile_user_account: AccountId,
        offset: u64,
        limit: u16,
        at: Option<Block::Hash>,
    ) -> RpcResult<Vec<ChallengePostId>> {
        let api = self.client.runtime_api();
        let at = at.unwrap_or_else(||
            // If the block hash is not supplied assume the best block.
            self.client.info().best_hash);

        let runtime_api_result =
            api.get_challengers_evidence(at, profile_user_account, offset, limit);
            fn map_err(error: impl ToString, desc: &'static str) -> CallError {
                CallError::Custom(ErrorObject::owned(
                    Error::RuntimeError.into(),
                    desc,
                    Some(error.to_string()),
                ))
            }
            let res = runtime_api_result.map_err(|e| map_err(e, "Unable to query dispatch info."))?;
            Ok(res)
    }