Macro sp_api::mock_impl_runtime_apis

mock_impl_runtime_apis!() { /* proc-macro */ }

Mocks given trait implementations as runtime apis.

Accepts similar syntax as impl_runtime_apis! and generates simplified mock implementations of the given runtime apis. The difference in syntax is that the trait does not need to be referenced by a qualified path, methods accept the &self parameter and the error type can be specified as associated type. If no error type is specified String is used as error type.

Besides implementing the given traits, the Core and ApiExt are implemented automatically.

Example

struct MockApi {
    balance: u64,
}

/// All runtime api mock implementations need to be done in one call of the macro!
sp_api::mock_impl_runtime_apis! {
    impl Balance<Block> for MockApi {
        /// Here we take the `&self` to access the instance.
        fn get_balance(&self) -> u64 {
            self.balance
        }
        fn set_balance(_bal: u64) {
            // Store the balance
        }
    }

    impl BlockBuilder<Block> for MockApi {
        fn build_block() -> Block {
             unimplemented!("Not Required in tests")
        }
    }
}

advanced attribute

This attribute can be placed above individual function in the mock implementation to request more control over the function declaration. From the client side each runtime api function is called with the at parameter that is a BlockId. When using the advanced attribute, the macro expects that the first parameter of the function is this at parameter. Besides that the macro also doesn’t do the automatic return value rewrite, which means that full return value must be specified. The full return value is constructed like Result<<ReturnValue>, Error> while ReturnValue being the return value that is specified in the trait declaration.

Example

struct MockApi {
    balance: u64,
}

sp_api::mock_impl_runtime_apis! {
    impl Balance<Block> for MockApi {
        #[advanced]
        fn get_balance(&self, at: &BlockId<Block>) -> Result<u64, sp_api::ApiError> {
            println!("Being called at: {}", at);

            Ok(self.balance.into())
        }
        #[advanced]
        fn set_balance(at: &BlockId<Block>, val: u64) -> Result<(), sp_api::ApiError> {
            if let BlockId::Number(1) = at {
                println!("Being called to set balance to: {}", val);
            }

            Ok(().into())
        }
    }
}