Smart contract development plays a crucial role in oracle development and enables the seamless integration of real-world data into blockchain networks. With smart contracts, oracles can securely and autonomously retrieve and verify external data. Let's explore the process of developing an oracle using an Ethereum smart contract.
Oracle Development Using Ethereum Smart Contracts
Oracles were created to enhance the possibilities of collaboration on blockchains. They establish connections between blockchains and external systems, enabling access to data from off-chain sources. Oracles act as a trusted source of information for the blockchain, providing secure gateways to off-chain systems. This allows smart contract applications to verify external events and trigger actions on external services.
Oracles essentially function as a link between two environments: the on-chain environment representing the blockchain network and the off-chain environment representing external systems in the real world.
pragma solidity >=0.7.0 <0.9.0;
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract EthPrice {
AggregatorV3Interface internal ethFeed;
bytes32 ethHash = keccak256(abi.encodePacked("ETH"));
constructor(_address) {
ethFeed = AggregatorV3Interface(_address);
}
function getEthPrice() public view returns (int) {(
uint80 roundID,
int price,
uint startedAt,
uint timeStamp,
uint80 answeredInRound
) = ethFeed.latestRoundData();
return price;
}
}
To get the address _address(Price feed contract address) of click here
Deploy the contract from the Deployment tab in Remix and run the function.
This code represents a Solidity smart contract called EthPrice that retrieves the latest price of Ethereum (ETH) using a Chainlink price feed.
Here's a breakdown of the code:
- The contract starts with SPDX-License-Identifier, which specifies the license under which the code is released.
- The pragma statement defines the version range of Solidity that the contract is compatible with.
- The import statement imports the AggregatorV3Interface from the Chainlink library. This interface provides functions to interact with Chainlink price feed contracts.
- The EthPrice contract has an internal variable ethFeed of type AggregatorV3Interface. It will be used to interact with the Chainlink price feed.
- The ethHash variable stores the keccak256 hash of the string "ETH". This can be used as an identifier or key for Ethereum.
- The constructor function is used to initialize the contract. It takes an _address parameter representing the address of the Chainlink price feed contract. It assigns the provided address to ethFeed.
- The getEthPrice function is a view function that retrieves the latest ETH price from the Chainlink price feed. It returns the price as an int.
- Inside the function, a tuple is defined to store the return values of the latestRoundData function from the ethFeed contract.
- The latestRoundData function fetches the latest round data from the Chainlink price feed.
- The price value is extracted from the tuple and returned.
In summary, the EthPrice contract interacts with a Chainlink price feed to retrieve the latest price of Ethereum (ETH) and provides a function getEthPrice to access this price from other contracts or externally.
Interested in Oracle development using smart contracts? Connect with our smart contract developers to get started.
If you’re new to all this cryptocurrency stuff, including smart contracts, ICOs, and TGEs (token generation events), check out our Guide to Blockchain Development to dip your toe in the water. If you find yourself wanting to learn more, look at the Ethereum Whitepaper.
If you already know what Ethereum and smart contracts are, but still have some points to clarify, then read on.
How does one make smart contracts and avoid mistakes? VironIT has experience in writing, testing, and deploying Ethereum smart contracts and its web interface. Over time we have collected questions and answers about smart contract development, so let’s dive right in!
I need pre-ICO and ICO. Should I have 1 or 2 contracts?
If the period between pre-ICO and ICO is short, it is more convenient to create a single smart contract for both pre-ICO and ICO.
If it takes more than a few months, then chances are everything will change considerably, to the point where you will have to create a new smart contract for the ICO phase.
Then the security issue must be considered. Two simple contracts are likely to be more robust than a large and complex one.
For example, project Hackspace Capital raised 18 000 ETH in September using one smart contract, and it worked perfectly for them (here is a video of an Ethereum Wallet our company recently finished for them).
Ethereum’s smart contracts are not easy to develop and are even more difficult to run and test, and the cost of failure is high.
Hackspace Capital is a platform established for investing in and developing early-stage technology hardware. It connects hardware startups identified by its strategic partner
How to update a deployed smart contract
Please note, Ethereum contracts are immutable. Once deployed to the blockchain, they cannot be updated. The only way to change the code is by destroying it altogether by the SELFDESTRUCT opcode (selfdestruct) (in solidity) and deploy everything again. Imagine how painful this could be having hundreds of backers already. You would have to mint all the tokens again, which may have a devastating impact on your online reputation and the whole ICO’s success.
How to write upgradable contracts in Solidity
To write an upgradable smart contract, you have to connect third-party libraries. However, using such contracts compromises security. This can be seen in the case with Parity, when about $150 million was locked in smart contracts delivered before 20 June 2017.
Some valuable functions to include in your Smart Contract
pause/unpause – to put on hold or resume token operations
setRate – to change token cost
mint – to charge tokens to the right address manually (for example, if you receive payment via bank transfer or in some other way)
changeOwner – to replace a contract holder
changeWallet – to replace an active wallet to receive tokens from a fallback function
How much can I raise? What are HardCap and SoftCap limits?
ICO is a limited time fundraising campaign. There are several variables that describe limits and time frames; these terms are hard cap, soft cap, and total supply.
Soft Cap is the minimum amount of funds required for the ICO to be considered successful.
Hard Cap is the maximum amount of funds raised. For example, if terms haven’t yet been reached, but the hard cap is already assembled, the company stops fundraising and project development starts.
Total supply is the total number of coins or tokens that are in existence, including those circulating in the public market and those that are locked or reserved.
Please consider the following points:
- What will happen with the unsold tokens at the stages of pre-ICO and ICO?
- What will happen if the soft cap is not achieved? How will they be refunded?
- Is it possible to issue additional tokens and, if so, on what conditions?
Should I limit token transfer?
Yes, you should. Please consider the following points:
- What is the amount of issued and mined tokens?
- Is there a limit on the release, as determined by the initial price of the tokens?
Be aware that a big player can derail the rate of your tokens on the stock exchange, buy them for next to nothing, and then resell them when the rate rebounds, so, it’s necessary to restrict the transfer of tokens in the pre-ICO / ICO and after the ICO period. But this will not resolve all the problems if you don’t make a right KYC, the process in which a business identifies and verifies the identity of its clients.
Token distribution
You should come up with a clear plan for the distribution of tokens, such as:
- 20% reserved for founders
- 15% for the purchase of data from data providers
- 60% goes on sale
- 2% for the Advisory Board
- 3% for the Bounty Program
Consider whether the distribution should be automatic or manual.
How to determine the start and end dates of pre-ICO/ICO
We advise you to avoid a fixed date for the start/finish in the smart contract. *hit happens and schedules shift.
That is why it is better to have manual control over the start and end of these events:
- Start pre-ICO / Stop pre-ICO
- Start ICO / Stop ICO
What’s the difference between utility and security tokens?
There are two types of tokens, utility tokens and security tokens.
Utility tokens drive the entire system. They allow one to develop features for the distributed ledger, access, and interaction with the system. They offer a vote in a meaningful way for free information and the possibility of exchanging opinions among token holders.
Security tokens represent a monetary investment in a startup, a share of profits, losses, assets, or liabilities. They offer status as an equity holder, creditor, or lender. Security tokens involve an expectation of profits consisting of dividends, periodic payments, and investment value. Profits are to be derived from the entrepreneurial or managerial efforts of others. Voting rights of the token holders don’t offer meaningful control over the startup.
For example, ICO Head Start uses utility token with a buyback program.
To summarize
Before working on contracts, you should consider their structure and regulation.
During contract development, you need to remember not only the typical techniques and programming issues, but also about the specifics of the blockchain. A thorough automated testing, auditing of contracts, as well as their code verification are all helpful and necessary to prevent errors from creeping into the contracts. Finish the development stage no later than 7 days before launch to give yourself enough time to ensure the code is faultless.
Whether you are a start-up or business seeking the help of an expert ICO advisor, VironIT will provide you with the means you need to take advantage of the crypto market.
Let us know if this article helped you or if you have any doubts. Please leave comments below if you have any questions.
As a refresh, the Ethereum adventure endeavors to help important dapps and brilliant contracts on the Ethereum blockchain, and the goal of the Ethereum Foundation is to connect developers with best-in-class R, build comprehension, and guidance.
A versatile technique to think of them as is an "In case that is clarification."
The Ethereum blockchain works comparatively as the Bitcoin blockchain: an arrangement of PCs run programming that supports trades through larger part accord.
Ethereum is at present driving the decentralized upheaval.
Ethereum won't not be as normal as the web as we likely am mindful it today, yet, anyone with a PC or a phone can endeavor the phase out as long as they have 'ether' - extraordinary bits of code that empower updates to the blockchain's record.
One reprobation is that losing your private key is a significantly more noteworthy course of action than losing a secret phrase: it infers losing your ether, until the finish of time.
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