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Create a Flow stream

In this guide, we will show you how you can create a Flow stream using Solidity.

It is important to note that A Flow stream has no end date, which means it will continue to accumulate debt even if no funds are deposited.

This guide assumes that you have already gone through the Calculate Rate per Second section.

caution

The code in this guide is not production-ready, and is implemented in a simplistic manner for the purpose of learning.

Set up a contract​

Declare the Solidity version used to compile the contract:

pragma solidity >=0.8.22;

Import the relevant symbols from @sablier/flow, and the FlowUtilities library:

import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
import { UD21x18 } from "@prb/math/src/UD21x18.sol";
import { ISablierFlow } from "@sablier/flow/src/interfaces/ISablierFlow.sol";

import { FlowUtilities } from "./FlowUtilities.sol";

Create a contract called FlowStreamCreator, and declare a constant USDC of type IERC20 and a constant FLOW of type ISablierFlow:

contract FlowStreamCreator {
    IERC20 public constant USDC = IERC20(0xf08A50178dfcDe18524640EA6618a1f965821715);
    ISablierFlow public constant FLOW = ISablierFlow(0x3a1beA13A8C24c0EA2b8fAE91E4b2762A59D7aF5);
}

In the code above, the contract addresses are hard-coded for demonstration purposes. However, in production, you would likely use input parameters to allow flexibility in changing the addresses.

Also, these addresses are deployed on Sepolia. If you need to work with a different chain, Flow addresses can be obtained from the Deployment Addresses page.

We will declare two functions, based on the amount desired to stream over a period of time.

Define a function​

Define a function to stream a salary of 1000 USDC per month, call it createStream_1K_PerMonth which returns the newly created stream ID:

function createStream_1K_PerMonth() external returns (uint256) {
    // ...
}

Input parameters​

Rate Per Second​

Use the FlowUtilities library to calculate the rate per second for the desired amount:

UD21x18 ratePerSecond = FlowUtilities.ratePerSecondWithDuration({ token: address(USDC), amount: 1000e6, duration: 30 days });

Sender​

The address streaming the tokens, with the ability to pause the stream:

sender = msg.sender

Recipient​

The address receiving the tokens:

recipient = address(0xCAFE);

Token​

The contract address of the ERC-20 token used for streaming. In this example, we will stream USDC:

token = USDC;

Transferable​

Boolean that indicates whether the stream will be transferable or not.

transferable = true;

Invoke the create function​

With all the parameters, we can call the create function on the FLOW contract and assign the newly created stream to streamId variable:

streamId = FLOW.create({
    sender: msg.sender,
    recipient: address(0xCAFE),
    ratePerSecond: FlowUtilities.ratePerSecondWithDuration({ token: address(USDC), amount: 1000e6, duration: 30 days }),
    token: USDC,
    transferable: true
});

Full code​

Below you can see the complete FlowStreamCreator contract:

Flow Stream Creator
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