This section guides you through deploying a Hello World smart contract using and on the Opera testnet.
If you have any questions, reach out in the .
Deploy an Opera Testnet Node
You need a node to deploy a smart contract to the chain. To get your node:
.
.
.
Install Foundry
Foundry is a development toolkit to work with smart contracts.
.
.
Initialize With Foundry
In your project directory, run foundry init. This will create a boilerplate project.
Fund Your Account
Create the Hello World Contract
In the initialized Foundry project in src/, create HelloWorld.sol:
// SPDX-License-Identifier: None
// Specifies the version of Solidity, using semantic versioning.
// Learn more: https://solidity.readthedocs.io/en/v0.5.10/layout-of-source-files.html#pragma
pragma solidity >=0.8.9;
// Defines a contract named `HelloWorld`.
// A contract is a collection of functions and data (its state). Once deployed, a contract resides at a specific address on the Fantom blockchain. Learn more: https://solidity.readthedocs.io/en/v0.5.10/structure-of-a-contract.html
contract HelloWorld {
//Emitted when update function is called
//Smart contract events are a way for your contract to communicate that something happened on the blockchain to your app front-end, which can be 'listening' for certain events and take action when they happen.
event UpdatedMessages(string oldStr, string newStr);
// Declares a state variable `message` of type `string`.
// State variables are variables whose values are permanently stored in contract storage. The keyword `public` makes variables accessible from outside a contract and creates a function that other contracts or clients can call to access the value.
string public message;
// Similar to many class-based object-oriented languages, a constructor is a special function that is only executed upon contract creation.
// Constructors are used to initialize the contract's data. Learn more:https://solidity.readthedocs.io/en/v0.5.10/contracts.html#constructors
constructor(string memory initMessage) {
// Accepts a string argument `initMessage` and sets the value into the contract's `message` storage variable).
message = initMessage;
}
// A public function that accepts a string argument and updates the `message` storage variable.
function update(string memory newMessage) public {
string memory oldMsg = message;
message = newMessage;
emit UpdatedMessages(oldMsg, newMessage);
}
}
Deploy the Contract
At this point, you are ready to deploy your contract:
You have your own node on the Opera testnet through which you will deploy the contract.
You have Foundry that you will use to deploy the contract.
You have a funded account that will deploy the contract.
