# Cast Vote

The `castVote` function allows an eligible voter to cast their approval or disapproval on a governance proposal. The voting power of an account is determined based on the number of votes delegated to it at the time the proposal transitioned into the Active state.

### Function Implementation in `CHNGovernance`

The `castVote()` function ensures that only eligible voters can participate in governance decisions, maintaining the integrity of the Onyx governance system.

#### Function Signature

```
function castVote(uint proposalId, bool support) public
```

Parameters

* `proposalId`: The unique identifier of the governance proposal on which the vote is being cast.
* `support`: A boolean value indicating the vote choice:
  * true → Vote in favor of the proposal (Yes)
  * false → Vote against the proposal (No)
* `RETURN`: The function does not return a value. If the proposal ID is invalid or the voter is ineligible, the transaction reverts with an error.

#### Example Solidity Implementation

To cast a vote using Solidity, the `castVote()` function can be called from an instance of the `CHNGovernance` contract:

```
CHNGovernance gov = CHNGovernance(0x123...); // Contract address of CHNGovernance
gov.castVote(proposalId, true); // Voting in favor of the proposal
```

#### Web3.js Implementation (v1.2.6)

For interacting with the `CHNGovernance` contract using Web3.js, the following example demonstrates how to cast a vote:

{% code overflow="wrap" %}

```javascript
const tx = await gov.methods.castVote(proposalId, false).send({ from: sender }); // Voting against the proposal
```

{% endcode %}

#### Technical Considerations

* The `castVote()` function is state-modifying and will incur gas costs.
* Votes are weighted based on the voting power at the moment the proposal became Active.
* If the voter has not been delegated voting power, they cannot cast a vote.
* Once a vote is cast, it cannot be changed unless the `castVoteWithReason` function (if available) is used.
* Proposal outcomes depend on the total votes cast before the voting period ends.
* Governance dashboards and vote tracking tools should integrate this function to allow real-time monitoring of voting activity.