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](https://raw.githubusercontent.com/Techbridge3/docs/master/docs/3.tutorials/examples/./advanced-xcc)
Obtaining the Cross Contract Call Example
You have two options to start the project:
- You can use the app through
Github Codespaces
, which will open a web-based interactive environment. - Clone the repository locally and use it from your computer.
Codespaces | Clone locally |
---|---|
🌠https://github.com/near-examples/cross-contract-calls |
Structure of the Example
The smart contract is available in two flavors: Rust and JavaScript
“`bash
┌── sandbox-ts # sandbox testing
│ ├── hello-near
│ │ └── hello-near.wasm
│ └── main.ava.ts
├── src # contract’s code
│ └── contract.ts
├── package.json
├── README.md
└── tsconfig.json
“`
“`bash
┌── tests # sandbox testing
│ ├── hello-near
│ │ └── hello-near.wasm
│ └── tests.rs
├── src # contract’s code
│ ├── external.rs
│ └── lib.rs
├── Cargo.toml # package manager
├── README.md
└── rust-toolchain.toml
“`
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.
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:
“`bash
cd contract-simple-ts
yarn
yarn test
“`
“`bash
cd contract-simple-rs
cargo test
“`
he `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.
Deploying the Contract to the NEAR network
In order to deploy the contract you will need to create a NEAR account.
“`bash
# Create a new account pre-funded by a faucet
near create-account
“`
“`bash
# Create a new account pre-funded by a faucet
near account create-account sponsor-by-faucet-service
“`
Go into the directory containing the smart contract (cd contract-advanced-ts
or cd contract-advanced-rs
), build and deploy it:
cargo near build
cargo near deploy <accountId> with-init-call new json-args '{"hello_account":"hello.near-example.testnet"}' prepaid-gas '100.0 Tgas' attached-deposit '0 NEAR' network-config testnet sign-with-keychain send
CLI: Interacting with the Contract
To interact with the contract through the console, you can use the following commands:
“`bash
# Get message from the hello-near contract
# Replace
near call
# Set a new message for the hello-near contract
# Replace
near call
“`
“`bash
# Get message from the hello-near contract
# Replace
near contract call-function as-transaction
# Set a new message for the hello-near contract
# Replace
near contract call-function as-transaction
“`
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`