Experiment with Data Feeds using Starknet Foundry and Starknet Devnet RS

This guide employs Starknet Devnet RS, a local Docker-based testnet environment for Starknet. It provides code examples and scripts that enable you to compile, declare, and deploy your own aggregator and consumer contracts. You can use a set of prefunded accounts to interact with Chainlink Data Feeds on Starknet without deploying to a live network.

Requirements

Set up your environment

This guide uses the Starknet Foundry toolkit and the Scarb project management tool so you can compile, deploy, and interact with your Starknet smart contracts.

Starknet Foundry: Install Starknet Foundry v0.21.0. You can check your current version by running snforge --version or sncast --version in your terminal and install the required version if necessary.
Scarb: Install Scarb v2.6.4. You can check your current version by running scarb --version in your terminal and install the required version if necessary.

Alternatively, you can use the asdf tool version manager to install both Starknet Foundry and Scarb. Read the setup instructions for Starknet Foundry and Scarb for more information.

Docker: Install Docker Desktop. You will run Starknet Devnet RS in a Docker container.

Clone and configure the code examples repository

Clone the chainlink-starknet repository, which includes the example contracts for this guide:
```
git clone https://github.com/smartcontractkit/chainlink-starknet.git
```

Navigate to the aggregator_consumer directory:

cd chainlink-starknet/examples/contracts/aggregator_consumer/

Open your snfoundry.toml file and locate the [sncast.devnet] section. Make sure the url points to the correct endpoint for connecting to the Starknet node running inside the Docker container. By default, it is:
```
[sncast.default]
url = "http://127.0.0.1:5050/rpc"
```

After you prepare the requirements, check to make sure the required tools are configured correctly by running the tests:

snforge test

The contracts should compile successfully and the tests should pass.

Tutorial

Run Starknet Devnet RS and add a prefunded account

Make sure Docker Desktop is running.
Execute the following command to run a Starknet Devnet RS container:
```
make devnet
```
Note: Executing this command when a container is running stops and recreates the container, which helps restart from a clean state.

The Starknet devnet container includes a set of prefunded accounts. To run the scripts from this guide, add one of these accounts to a local accounts.json file using the following command:

make add-account

Expect an output similar to the following:

Importing a prefunded account from starknet devnet container...

command: account add

Your accounts:

{
"alpha-goerli": {
   "devnet-account": {
      "address": "0x4b3f4ba8c00a02b66142a4b1dd41a4dfab4f92650922a3280977b0f03c75ee1",
      "class_hash": "0x61dac032f228abef9c6626f995015233097ae253a7f72d68552db02f2971b8f",
      "deployed": true,
      "legacy": false,
      "private_key": "0x57b2f8431c772e647712ae93cc616638",
      "public_key": "0x374f7fcb50bc2d6b8b7a267f919232e3ac68354ce3eafe88d3df323fc1deb23"
   }
}
}

Deploy and interact with a mock aggregator contract

Declare and deploy a mock aggregator contract to the devnet by using the deploy_mock_aggregator script. Run the following command:
```
make ma-deploy NETWORK=devnet
```
Expect an output similar to the following:
```
Declaring and deploying MockAggregator
Declaring contract...
Transaction hash = 0x568d29d07128cba750845b57a4bb77a31f628b6f4288861d8b31d12e71e4c3b
Deploying contract...
Transaction hash = 0xfbc49eb82894a704ce536ab904cdee0fd021b0fba335900f8b9b12cfcd005f
MockAggregator deployed at address: 1566652744716179301065270359129119857774335542042051464747302084192731701184

command: script run
status: success
```
Save the mock aggregator contract address for later. In this example, it is 1566652744716179301065270359129119857774335542042051464747302084192731701184 (decimal representation), equivalent to 0x376B1ABF788737BDED2011A0F76CE61CABDEAEC22E97B8A4E231B149DD49FC0 (hexadecimal representation). You can use a decimal-to-hexadecimal converter to convert the address.
Read the latest round data by using the read_latest_round script. Run the following command:
```
make agg-read-latest-round NETWORK=devnet
```
Expect an output similar to the following:
```
Result::Ok(CallResult { data: [0, 0, 0, 0, 0] })
command: script run
status: success
```
By default, the retrieved data from your mock aggregator contract are all zeros.

You can set the latest round data using the set_latest_round script. Run the following command:

make ma-set-latest-round NETWORK=devnet

Expect an output similar to the following:

Transaction hash = 0x3f01f4595dcf20b4f355720540d5279efc0fff306d4e848dda4550cdd2a5367
Result::Ok(InvokeResult { transaction_hash: 1781197671452105104356220458359085564429259248315865550090042149835146679143 })
command: script run
status: success

Read the latest round data again using the make agg-read-latest-round NETWORK=devnet command to verify the updated values:
```
Result::Ok(CallResult { data: [1, 1, 12345, 100000, 200000] })
command: script run
status: success
```

Deploy and interact with a mock aggregator and a mock consumer contract

The mock aggregator consumer contract is initialized with the address of an aggregator mock contract during the contract's constructor call and contains two functions:

set_answer retrieves the latest answer from the specified aggregator contract and stores it in the internal storage variable _answer.
read_answer reads the stored _answer value.

Run the following command to (re)start the Starknet Devnet RS container:
```
make devnet
```
Add a prefunded account to the local accounts.json file using the following command:
```
make add-account
```

Declare and deploy both a mock aggregator and a consumer contracts to the devnet using the following command:

make devnet-deploy

This command runs both deploy_mock_aggregator and deploy_aggregator_consumer scripts.

Expect an output similar to the following:

Declaring and deploying MockAggregator
Declaring contract...
Transaction hash = 0x568d29d07128cba750845b57a4bb77a31f628b6f4288861d8b31d12e71e4c3b
Deploying contract...
Transaction hash = 0xfbc49eb82894a704ce536ab904cdee0fd021b0fba335900f8b9b12cfcd005f
MockAggregator deployed at address: 1566652744716179301065270359129119857774335542042051464747302084192731701184

command: script run
status: success

Declaring and deploying AggregatorConsumer
Declaring contract...
Transaction hash = 0x3f11f08103e263690b1eeac76c25ce7b003c86d2d1c0492815d1ddb39f58e8e
Deploying contract...
Transaction hash = 0xfe5b1ed51a435117098343b5d0fdc1c32fd493f1220ff2c69c732f5bb805d8
AggregatorConsumer deployed at address: 2775662320989421053891107164335108610292525354452508848326323790006553228656

command: script run
status: success

Once the contracts are deployed, experiment with both contracts and the available scripts and commands as needed for your projects.

For instance, you can set new values for the latest round of data on the aggregator contract, retrieve and set the answer on the consumer contract, and read the answer from the consumer contract:

make ma-set-latest-round NETWORK=devnet && make ac-set-answer NETWORK=devnet && make ac-read-answer NETWORK=devnet

Experiment with Data Feeds using Starknet Foundry and Starknet Devnet RS

Requirements

Set up your environment

Clone and configure the code examples repository

Tutorial

Run Starknet Devnet RS and add a prefunded account

Deploy and interact with a mock aggregator contract

Deploy and interact with a mock aggregator and a mock consumer contract

What's next

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