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Version: 4.22.0

Interact with your contract

Once your provider, contract and account are connected, you can interact with the contract :

  • you can read the memory of the contract, without fees.
  • you can write to memory, but you have to pay fees.
    • On Mainnet, you have to pay fees with bridged ETH token.
    • On Testnet 1 & 2, you have to pay with bridged Goerli ETH token.
    • On devnet, you have to pay with dummy ETH token.

Your account should be funded enough to pay fees (0.01 ETH should be enough to start).

Here we will interact with a test.cairo contract, already deployed in Testnet 1 and Tesnet 2, at addresses :

We will use Testnet1, so you need a funded wallet in this network.

This contract contains a storage memory called balance.

  • It can be read with the @view function : get_balance()
  • Balance can be modified with the @external function : increase_balance(amount1: felt, amount2: felt)
import { Provider, Contract, Account, ec, json } from "starknet";

🔍 Read contract memory, with call​

To read the balance, you need only to connect a Provider and a Contract.
You have to use the call function : contract.call("function_name",[params]) (here params is not necessary, because there are no parameters for the get_balance function).

//initialize Provider
const provider = new Provider({ sequencer: { network: "goerli-alpha" } });
// Connect the deployed Test contract in Tesnet
const testAddress = "0x5f7cd1fd465baff2ba9d2d1501ad0a2eb5337d9a885be319366b5205a414fdd";

// read abi of Test contract
const { abi: testAbi } = await provider.getClassAt(testAddress);
if (testAbi === undefined) { throw new Error("no abi.") };
const myTestContract = new Contract(testAbi, testAddress, provider);

// Interaction with the contract with call
const bal1 = await myTestContract.call("get_balance");
console.log("Initial balance =", bal1.res.toString()); // .res because the  return value is called 'res' in the cairo contract

✍️ Write contract memory, with invoke​

To increase the balance, you need in addition a connected and funded Account.

You have to use the invoke function : contract.invoke("function_name",[params]) After the invoke function, you have to wait the incorporation of the modification of Balance in the network, with await provider.waitForTransaction(transaction_hash)

Here is an example to increase and check the balance :

//initialize Provider
const provider = new Provider({ sequencer: { network: "goerli-alpha" } });
// connect your account. To adapt to your own account :
const privateKey0 = process.env.OZ_ACCOUNT_PRIVATE_KEY;
const account0Address = "0x123....789";

const starkKeyPair0 = ec.getKeyPair(privateKey0);
const account0 = new Account(provider, account0Address, starkKeyPair0);

// Connect the deployed Test contract in Tesnet
const testAddress = "0x5f7cd1fd465baff2ba9d2d1501ad0a2eb5337d9a885be319366b5205a414fdd";

// read abi of Test contract
const { abi: testAbi } = await provider.getClassAt(testAddress);
if (testAbi === undefined) { throw new Error("no abi.") };
const myTestContract = new Contract(testAbi, testAddress, provider);

// Connect account with the contract
myTestContract.connect(account0);

// Interactions with the contract with call & invoke
const bal1 = await myTestContract.call("get_balance");
console.log("Initial balance =", bal1.res.toString());
const res = await myTestContract.invoke("increase_balance", [10, 30]);

await provider.waitForTransaction(res.transaction_hash);
const bal2 = await myTestContract.call("get_balance");
console.log("Initial balance =", bal2.res.toString());

Use meta-class of Contract​

You have another way to interact with a contract - the meta-class : each Contract object as specific functions to interact. For example here, we have 2 additional functions for the Test contract object:

  • Contract.get_balance()
  • Contract.increase_balance()

The code can be modified this way :

//initialize Provider
const provider = new Provider({ sequencer: { network: "goerli-alpha" } });
// connect your account. To adapt to your own account :
const privateKey0 = process.env.OZ_ACCOUNT_PRIVATE_KEY;
const account0Address = "0x123....789";

const starkKeyPair0 = ec.getKeyPair(privateKey0);
const account0 = new Account(provider, account0Address, starkKeyPair0);

// Connect the deployed Test contract in Tesnet
const testAddress = "0x5f7cd1fd465baff2ba9d2d1501ad0a2eb5337d9a885be319366b5205a414fdd";

// read abi of Test contract
const { abi: testAbi } = await provider.getClassAt(testAddress);
if (testAbi === undefined) { throw new Error("no abi.") };
const myTestContract = new Contract(testAbi, testAddress, provider);

// Connect account with the contract
myTestContract.connect(account0);

// Interactions with the contract with call & invoke
const bal1 = await myTestContract.get_balance();
console.log("Initial balance =", bal1.res.toString());

const resu = await myTestContract.increase_balance(10, 30);
await provider.waitForTransaction(resu.transaction_hash);

const bal2 = await myTestContract.get_balance();import { Provider, Contract, Account, ec, json } from "starknet";
console.log("Initial balance =", bal2.res.toString());

Write to contract memory, with Account.execute​

If you have to invoke a function of a contract that need the proof that you have the private key of the account, you have to invoke this function with account.execute.

We will see this case more in detail in ERC20 scripts, but in summary, you use this command with the following parameters:

  • address of the contract to invoke
  • name of the function to invoke
  • and array of parameters for this function
const executeHash = await account.execute(
  {
    contractAddress: myContractAddress,
    entrypoint: 'transfer',
    calldata: stark.compileCalldata({
      recipient: receiverAddress,
      amount: ['10']
    })
  }
);
await provider.waitForTransaction(executeHash.transaction_hash);