How to make a Chainlinked contract

Creating Chainlinked Contracts

Making your contract "Chainlinked" allows the contract to request data from the Chainlink network. Feel free to ask us on Gitter if you have any questions!

Adding Chainlink to your project

The required contracts can be added to your project by using the following command:

$ yarn add github:smartcontractkit/chainlink

Importing Chainlinked

Once you've imported the Chainlinked.sol contract, your contract can inherit the Chainlinked behavior:

import "chainlink/solidity/contracts/Chainlinked.sol";

contract MyContract is Chainlinked {
...

Requesting data

Here is an example of a Chainlink request, called a run:

  function requestEthereumPrice(string _currency) public onlyOwner {
    ChainlinkLib.Run memory run = newRun(jobId, this, "requestedDataCallback(bytes32,uint256)");
    run.add("url", "https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=USD,EUR,JPY");
    string[] memory path = new string[](1);
    path[0] = _currency;
    run.addStringArray("path", path);
    requestId = chainlinkRequest(run, LINK(1));
  }

You give the JobID in the constructor of your contract or you can supply it as a parameter for your requesting function.

function requestEthereumPrice(string _currency, bytes32 jobId) public onlyOwner {
  ChainlinkLib.Run memory run = newRun(jobId, this, "requestedDataCallback(bytes32,uint256)");
  ...

Additionally, you may create a request without a JobID by building the tasks in the contract. Take note of the newSpec function used below:

  function requestEthereumPrice(string _currency) public {
    string[] memory tasks = new string[](4);
    tasks[0] = "httpget";
    tasks[1] = "jsonparse";
    tasks[2] = "ethint256";
    tasks[3] = "ethtx";

    ChainlinkLib.Spec memory spec = newSpec(tasks, this, "fulfill(bytes32,uint256)");
    spec.add("url", "https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=USD,EUR,JPY");
    string[] memory path = new string[](1);
    path[0] = _currency;
    spec.addStringArray("path", path);
    chainlinkRequest(spec, LINK(1));
  }

Cancelling an unfilfilled request

You may want the functionality to cancel a request, this is implemented through the deployed oracle contract:

  function cancelRequest(uint256 _requestId) 
    public
    ifAgreed(_requestId)
  {
    oracle.cancel(_requestId);
    ...

Receiving data

In the example above, requestedDataCallback is the callback method supplied in requestEthereumPrice.

  function requestedDataCallback(bytes32 _requestId, uint256 _price)
    public
    onlyOracle
    checkRequestId(_requestId)
  {
    emit RequestFulfilled(_requestId, _price);
    currentPrice = _price;
  }

  modifier checkRequestId(bytes32 _requestId) {
    require(requestId == _requestId);
    _;
  }

You can view additional examples of how to create Chainlinked contracts here.

Deploying to Ropsten

In order for a contract to make use of the Ropsten network, you'll need to have the address of the deployed Ropsten LINK token, and our oracle contract. The Ropsten LINK token's address is "0x20fE562d797A42Dcb3399062AE9546cd06f63280" and the oracle contract's address is "0x5be84B6381d45579Ed04A887B8473F76699E0389".

You will also need the JobID as bytes when invoking a new run. We have pre-made jobs available for you. Types with "x100" indicate that the value received from the given endpoint will be multiplied by 100 before being written to the blockchain. The string value of the JobIDs will need to be given to the Run as bytes.

Type	Job ID	Required Params
Uint256	5eadba6f077e4ca8ac88cc370eb66a5f	url(string), path(array of strings)
Uint256x100	d41a0bdf968a43aca8822cf81a2c1fa7	url(string), path(array of strings)
Bytes32	2660763707434f35bb58a9db33ee1803	url(string), path(array of strings)
Int256	cdda8f68cb3e4108a83977c9c600d3a7	url(string), path(array of strings)
Int256x100	9a888d17f766458d99dfea62588c8280	url(string), path(array of strings)