如何使用 Substrate API Client 写入 Substrate 的存储？

Question

My goal is to write a value in the storage map of Substrate using substrate-api-client . My storage map, defined in the Substrate chain, looks like this:

use frame_support::{decl_module, decl_storage, dispatch::result::Result, ensure, StorageMap};
use frame_system::ensure_signed;
use sp_runtime::DispatchError;

// pub trait Trait: balances::Trait {}
pub trait Trait: pallet_balances::Trait {}

decl_storage! {
    trait Store for Module<T: Trait> as KittyStorage {
        // Value: map T::Hash => Option<T::AccountId>;
        // TODO: check whether this is the appropriate datatype(hash).
        Value: map hasher(blake2_256) T::Hash => Option<T::AccountId>;
        // Balances: map hasher(blake2_256) (T::AssetId, T::AccountId) => T::Balance;
    }
}

decl_module! {
    pub struct Module<T: Trait> for enum Call where origin: T::Origin {
        fn set_value(origin, value: T::Hash) -> Result<(), DispatchError> {
            let sender = ensure_signed(origin)?;
            ensure!(!<Value<T>>::contains_key(value), "key already exists");
            <Value<T>>::insert(value, sender);
            Ok(())
        }
    }
}

The above storage map is located at:

substrate/bin/node/runtime/src/substratekitties.rs

The expected result is to successfully write a value on the Substrate's storage. As I do in the frontend, successfully:

However, while using the substrate-api-client to do the same task, I am getting the following error:

[2020-04-03T05:14:12Z ERROR substrate_api_client::rpc::client] ERROR: Object({"code": Number(1010), "data": String("BadProof"), "message": String("Invalid Transaction")})

I have tried to write a custom extrinsic example in the substrate-api-client . This is how I am composing the extrinsic:

let xt = compose_extrinsic!(
        api.clone(),
        "Substratekitties",
        "set_value",
        "0x0000000000000000000000000000000000000000000000000000000000000002"
    );

This is the minimal code required to reproduce the error:

/*
    Copyright 2019 Supercomputing Systems AG
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

//! This examples shows how to use the compose_extrinsic macro to create an extrinsic for any (custom)
//! module, whereas the desired module and call are supplied as a string.

use clap::{load_yaml, App};
use keyring::AccountKeyring;
use sp_core::crypto::Pair;
// use substrate_api_client::extrinsic::xt_primitives::UncheckedExtrinsicV4;
use substrate_api_client::{
    compose_extrinsic, extrinsic::xt_primitives::UncheckedExtrinsicV4, Api,
};

// use crate::{compose_extrinsic, Api};

fn main() {
    env_logger::init();
    let url = get_node_url_from_cli();
    // initialize api and set the signer (sender) that is used to sign the extrinsics
    let from = AccountKeyring::Alice.pair();
    let mut api = Api::new(format!("ws://{}", url)).set_signer(from);
    // let signer = AccountKeyring::Alice.pair();
    // api.signer = Some(signer);
    // the names are given as strings
    let xt = compose_extrinsic!(
        api.clone(),
        "Substratekitties",
        "set_value",
        "0x0000000000000000000000000000000000000000000000000000000000000002"
    );
    println!("[+] Composed Extrinsic:\n {:?}\n", xt);
    // send and watch extrinsic until finalized
    let signer = AccountKeyring::Alice.pair();
    api.signer = Some(signer);
    let tx_hash = api.send_extrinsic(xt.hex_encode()).unwrap();
    println!("[+] Transaction got finalized. Hash: {:?}", tx_hash);
}

pub fn get_node_url_from_cli() -> String {
    let yml = load_yaml!("../../src/examples/cli.yml");
    let matches = App::from_yaml(yml).get_matches();

    let node_ip = matches.value_of("node-server").unwrap_or("127.0.0.1");
    let node_port = matches.value_of("node-port").unwrap_or("9944");
    let url = format!("{}:{}", node_ip, node_port);
    println!("Interacting with node on {}\n", url);
    url
}

The above code is located in the file: example_writing_file_hash.rs and the tree is:

substrate-api-client/src/examples/example_writing_file_hash.rs

whereas the complete codebase is available here .

Update 1

As per user13207835 's answer , I tried declaring my content as a hash but failed. PS I am a beginner in Rust, Substrate.

let file_hash: Hash = "0x0000000000000000000000000000000000000000000000000000000000000002";

Got the error:

error[E0308]: mismatched types; expected struct `primitive_types::H256`, found `&str`

I understand this error, though I am unaware of how to declare the above value as Hash as suggested in the answer.

Answer 1

You declare your function as fn set_value(origin, value: T::Hash) . Thus, you must pass a Hash to the compose_extrinsic! macro as it does simply encode the arguments as they are passed. It does not know that "0x...2" is a hash. Hence, it will encode it as a string.

Therefore, you should be passing a something, whose raw data is encoded the same as the Hash representation in your node. There are two options:

• Just use an [u8, 32] array.
• Use the Hash from one of the primitives crate from substrate