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Cross Contract Call

This example performs the simplest cross-contract call possible: it calls our Hello NEAR example to set and retrieve a greeting. It is one of the simplest examples on making a cross-contract call, and the perfect gateway to the world of interoperative contracts.

Advanced Cross-Contract Calls Check the tutorial on how to perform cross-contract calls in batches and in parallel :::

Obtaining the Cross Contract Call Example​

You have two options to start the project:

  1. You can use the app through Github Codespaces, which will open a web-based interactive environment.
  2. Clone the repository locally and use it from your computer.
CodespacesClone locally
Open in GitHub Codespaces🌐 https://github.com/near-examples/cross-contract-calls

Structure of the Example​

The smart contract is available in two flavors: Rust and JavaScript

┌── sandbox-ts # sandbox testing
│    ├── hello-near
│    │    └── hello-near.wasm
│    └── main.ava.ts
├── src # contract's code
│    └── contract.ts
├── package.json
├── README.md
└── tsconfig.json

Smart Contract​

Contract​

The contract exposes methods to query the greeting and change it. These methods do nothing but calling get_greeting and set_greeting in the hello-near example.

contract-simple-ts/src/contract.ts
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Testing the Contract​

The contract readily includes a set of unit and sandbox testing to validate its functionality. To execute the tests, run the following commands:

cd contract-simple-ts
yarn
yarn test
The integration tests use a sandbox to create NEAR users and simulate interactions with the contract. :::

In this project in particular, the integration tests first deploy the hello-near contract. Then, they test that the cross-contract call correctly sets and retrieves the message. You will find the integration tests in sandbox-ts/ for the JavaScript version and in tests/ for the Rust version.

contract-simple-ts/sandbox-ts/main.ava.ts
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Deploying the Contract to the NEAR network​

In order to deploy the contract you will need to create a NEAR account.

# Optional - create an account
near create-account <accountId> --useFaucet

# Deploy the contract
cd contract-simple-ts
yarn build
near deploy <accountId> ./build/cross_contract.wasm init --initFunction init --initArgs '{"hello_account":"hello.near-example.testnet"}'

CLI: Interacting with the Contract​

To interact with the contract through the console, you can use the following commands:

# Get message from the hello-near contract
# Replace <accountId> with your account ID
near call <accountId> query_greeting --accountId <accountId>

# Set a new message for the hello-near contract
# Replace <accountId> with your account ID
near call <accountId> change_greeting '{"new_greeting":"XCC Hi"}' --accountId <accountId>

Moving Forward​

A nice way to learn is by trying to expand a contract. Modify the cross contract example to use the guest-book contract!. In this way, you can try to make a cross-contract call that attaches money. Remember to correctly handle the callback, and to return the money to the user in case of error.

Advanced Cross Contract Calls​

Your contract can perform multiple cross-contract calls in simultaneous, creating promises that execute in parallel, or as a batch transaction. Check the advanced cross contract calls tutorial to learn more.

Versioning for this article

At the time of this writing, this example works with the following versions:

  • near-cli: 4.0.13
  • node: 18.19.1
  • rustc: 1.77.0
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