Remote type

Your contract may rely on communication with another one. For example, it could instantiate a CW20 contract and, during the workflow, send Mint messages to it. If CW20 contract was created using sylvia, it would have a Remote type generated which would make this process more user friendly. Currently, it is only possible to send queries using Remote but support for the execute messages is on the way.

To check some examples, checkout the sylvia repository and go to sylvia/tests/remote.rs.

Working with Remote

Remote represents some contract instantiated on the blockchain. It aims to give contract developers a gateway to communicate with other contracts. It has only one field, which is a remote contract address. It exposes only a single method called querier, which returns a BoundQuerier type. BoundQuerier has a method for every contract and interface query. If we create a contract relying on our CounterContract, it could query its state as below.

let count = Remote::<CounterContract>::new(addr)
    .querier(&ctx.deps.querier)
    .count()?
    .count;

let admins = crate::whitelist::Remote::<CounterContract>::new(ctx.info.sender)
    .querier(&ctx.deps.querier)
    .admins()?;

Important to note is that Remote is generic over the contract type. To use it in context of some contract, just initialize it generic over it.

In case of contract initializing the CW20 contract you might want to keep its address in the state.

use sylvia::types::Remote;

struct Contract<'a> {
    cw20: Item<Remote<'a, Cw20Contract>>,
}

Then to query the contract load the remote, call querier on it which will return BoundQuerier and then call the query method on it.

self.cw20
    .load(ctx.deps.storage)?
    .querier(&ctx.deps.querier)
    .query_all_balances()?

Next step

Phew.. that was a journey. We learned most of the sylvia features and should be ready to create our first contracts. In the last chapter, we will learn about some of the best practices that will make our code more readable and maintainable.