More on NFTs & Art

shivsak
3 years ago
A visual exploration of the REAL use cases for NFTs in the Future
In this essay, I studied REAL NFT use examples and their potential uses.
Knowledge of the Hype Cycle
Gartner's Hype Cycle.
It proposes 5 phases for disruptive technology.
1. Technology Trigger: the emergence of potentially disruptive technology.
2. Peak of Inflated Expectations: Early publicity creates hype. (Ex: 2021 Bubble)
3. Trough of Disillusionment: Early projects fail to deliver on promises and the public loses interest. I suspect NFTs are somewhere around this trough of disillusionment now.
4. Enlightenment slope: The tech shows successful use cases.
5. Plateau of Productivity: Mainstream adoption has arrived and broader market applications have proven themselves. Here’s a more detailed visual of the Gartner Hype Cycle from Wikipedia.
In the speculative NFT bubble of 2021, @beeple sold Everydays: the First 5000 Days for $69 MILLION in 2021's NFT bubble.
@nbatopshot sold millions in video collectibles.
This is when expectations peaked.
Let's examine NFTs' real-world applications.
Watch this video if you're unfamiliar with NFTs.
Online Art
Most people think NFTs are rich people buying worthless JPEGs and MP4s.
Digital artwork and collectibles are revolutionary for creators and enthusiasts.
NFT Profile Pictures
You might also have seen NFT profile pictures on Twitter.
My profile picture is an NFT I coined with @skogards factoria app, which helps me avoid bogus accounts.
Profile pictures are a good beginning point because they're unique and clearly yours.
NFTs are a way to represent proof-of-ownership. It’s easier to prove ownership of digital assets than physical assets, which is why artwork and pfps are the first use cases.
They can do much more.
NFTs can represent anything with a unique owner and digital ownership certificate. Domains and usernames.
Usernames & Domains
@unstoppableweb, @ensdomains, @rarible sell NFT domains.
NFT domains are transferable, which is a benefit.
Godaddy and other web2 providers have difficult-to-transfer domains. Domains are often leased instead of purchased.
Tickets
NFTs can also represent concert tickets and event passes.
There's a limited number, and entry requires proof.
NFTs can eliminate the problem of forgery and make it easy to verify authenticity and ownership.
NFT tickets can be traded on the secondary market, which allows for:
marketplaces that are uniform and offer the seller and buyer security (currently, tickets are traded on inefficient markets like FB & craigslist)
unbiased pricing
Payment of royalties to the creator
4. Historical ticket ownership data implies performers can airdrop future passes, discounts, etc.
5. NFT passes can be a fandom badge.
The $30B+ online tickets business is increasing fast.
NFT-based ticketing projects:
Gaming Assets
NFTs also help in-game assets.
Imagine someone spending five years collecting a rare in-game blade, then outgrowing or quitting the game. Gamers value that collectible.
The gaming industry is expected to make $200 BILLION in revenue this year, a significant portion of which comes from in-game purchases.
Royalties on secondary market trading of gaming assets encourage gaming businesses to develop NFT-based ecosystems.
Digital assets are the start. On-chain NFTs can represent real-world assets effectively.
Real estate has a unique owner and requires ownership confirmation.
Real Estate
Tokenizing property has many benefits.
1. Can be fractionalized to increase access, liquidity
2. Can be collateralized to increase capital efficiency and access to loans backed by an on-chain asset
3. Allows investors to diversify or make bets on specific neighborhoods, towns or cities +++
I've written about this thought exercise before.
I made an animated video explaining this.
We've just explored NFTs for transferable assets. But what about non-transferrable NFTs?
SBTs are Soul-Bound Tokens. Vitalik Buterin (Ethereum co-founder) blogged about this.
NFTs are basically verifiable digital certificates.
Diplomas & Degrees
That fits Degrees & Diplomas. These shouldn't be marketable, thus they can be non-transferable SBTs.
Anyone can verify the legitimacy of on-chain credentials, degrees, abilities, and achievements.
The same goes for other awards.
For example, LinkedIn could give you a verified checkmark for your degree or skills.
Authenticity Protection
NFTs can also safeguard against counterfeiting.
Counterfeiting is the largest criminal enterprise in the world, estimated to be $2 TRILLION a year and growing.
Anti-counterfeit tech is valuable.
This is one of @ORIGYNTech's projects.
Identity
Identity theft/verification is another real-world problem NFTs can handle.
In the US, 15 million+ citizens face identity theft every year, suffering damages of over $50 billion a year.
This isn't surprising considering all you need for US identity theft is a 9-digit number handed around in emails, documents, on the phone, etc.
Identity NFTs can fix this.
NFTs are one-of-a-kind and unforgeable.
NFTs offer a universal standard.
NFTs are simple to verify.
SBTs, or non-transferrable NFTs, are tied to a particular wallet.
In the event of wallet loss or theft, NFTs may be revoked.
This could be one of the biggest use cases for NFTs.
Imagine a global identity standard that is standardized across countries, cannot be forged or stolen, is digital, easy to verify, and protects your private details.
Since your identity is more than your government ID, you may have many NFTs.
@0xPolygon and @civickey are developing on-chain identity.
Memberships
NFTs can authenticate digital and physical memberships.
Voting
NFT IDs can verify votes.
If you remember 2020, you'll know why this is an issue.
Online voting's ease can boost turnout.
Informational property
NFTs can protect IP.
This can earn creators royalties.
NFTs have 2 important properties:
Verifiability IP ownership is unambiguously stated and publicly verified.
Platforms that enable authors to receive royalties on their IP can enter the market thanks to standardization.
Content Rights
Monetization without copyrighting = more opportunities for everyone.
This works well with the music.
Spotify and Apple Music pay creators very little.
Crowdfunding
Creators can crowdfund with NFTs.
NFTs can represent future royalties for investors.
This is particularly useful for fields where people who are not in the top 1% can’t make money. (Example: Professional sports players)
Mirror.xyz allows blog-based crowdfunding.
Financial NFTs
This introduces Financial NFTs (fNFTs). Unique financial contracts abound.
Examples:
a person's collection of assets (unique portfolio)
A loan contract that has been partially repaid with a lender
temporal tokens (ex: veCRV)
Legal Agreements
Not just financial contracts.
NFT can represent any legal contract or document.
Messages & Emails
What about other agreements? Verbal agreements through emails and messages are likewise unique, but they're easily lost and fabricated.
Health Records
Medical records or prescriptions are another types of documentation that has to be verified but isn't.
Medical NFT examples:
Immunization records
Covid test outcomes
Prescriptions
health issues that may affect one's identity
Observations made via health sensors
Existing systems of proof by paper / PDF have photoshop-risk.
I tried to include most use scenarios, but this is just the beginning.
NFTs have many innovative uses.
For example: @ShaanVP minted an NFT called “5 Minutes of Fame” 👇
Here are 2 Twitter threads about NFTs:
This piece of gold by @chriscantino
2. This conversation between @punk6529 and @RaoulGMI on @RealVision“The World According to @punk6529”
If you're wondering why NFTs are better than web2 databases for these use scenarios, see this Twitter thread I wrote:
If you liked this, please share it.

Tora Northman
3 years ago
Pixelmon NFTs are so bad, they are almost good!
Bored Apes prices continue to rise, HAPEBEAST launches, Invisible Friends hype continues to grow. Sadly, not all projects are as successful.
Of course, there are many factors to consider when buying an NFT. Is the project a scam? Will the reveal derail the project? Possibly, but when Pixelmon first teased its launch, it generated a lot of buzz.
With a primary sale mint price of 3 ETH ($8,100 USD), it started as an expensive project, with plenty of fans willing to invest in what was sold as a game. After it was revealed, it fell rapidly.
Why? It was overpromised and under delivered.
According to the project's creator[^1], the funds generated will be used to develop the artwork. "The Pixelmon reveal was wrong. This is what our Pixelmon look like in-game. "Despite the fud, I will not go anywhere," he wrote on Twitter. The goal remains. The funds will still be used to build our game. I will finish this project."
The project raised $70 million USD, but the NFTs buyers received were not the project's original teasers. Some call it "the worst NFT project ever," while others call it a complete scam.
But there's hope for some buyers. Kevin emerged from the ashes as the project was roasted over the fire.
A Minecraft character meets Salad Fingers - that's Kevin. He's a frog-like creature whose reveal was such a terrible NFT that it became part of history – and a meme.
If you're laughing at people paying $8K for a silly pixelated image, you might need to take it back. Precisely because of this, lucky holders who minted Kevin have been able to sell the now-memed NFT for over 8 ETH (around $24,000 USD), with some currently listed for 100 ETH.
Of course, Twitter has been awash in memes mocking those who invested in the project, because what else can you do when so many people lose money?
It's still unclear if the NFT project is a scam, but the team behind it was hired on Upwork. There's still hope for redemption, but Kevin's rise to fame appears to be the only positive outcome so far.
[^1] This is not the first time the creator (A 20-yo New Zealanders) has sought money via an online platform and had people claiming he under-delivered. He raised $74,000 on Kickstarter for a card game called Psycho Chicken. There are hundreds of comments on the Kickstarter project saying they haven't received the product and pleading for a refund or an update.

CyberPunkMetalHead
2 years ago
Why Bitcoin NFTs Are Incomprehensible yet Likely Here to Stay
I'm trying to understand why Bitcoin NFTs aren't ready.
Ordinals, a new Bitcoin protocol, has been controversial. NFTs can be added to Bitcoin transactions using the protocol. They are not tokens or fungible. Bitcoin NFTs are transaction metadata. Yes. They're not owned.
In January, the Ordinals protocol allowed data like photos to be directly encoded onto sats, the smallest units of Bitcoin worth 0.00000001 BTC, on the Bitcoin blockchain. Ordinals does not need a sidechain or token like other techniques. The Ordinals protocol has encoded JPEG photos, digital art, new profile picture (PFP) projects, and even 1993 DOOM onto the Bitcoin network.
Ordinals inscriptions are permanent digital artifacts preserved on the Bitcoin blockchain. It differs from Ethereum, Solana, and Stacks NFT technologies that allow smart contract creators to change information. Ordinals store the whole image or content on the blockchain, not just a link to an external server, unlike centralized databases, which can change the linked image, description, category, or contract identifier.
So far, more than 50,000 ordinals have been produced on the Bitcoin blockchain, and some of them have already been sold for astronomical amounts. The Ethereum-based CryptoPunks NFT collection spawned Ordinal Punk. Inscription 620 sold for 9.5 BTC, or $218,000, the most.
Segwit and Taproot, two important Bitcoin blockchain updates, enabled this. These protocols store transaction metadata, unlike Ethereum, where the NFT is the token. Bitcoin's NFT is a sat's transaction details.
What effects do ordinary values and NFTs have on the Bitcoin blockchain?
Ordinals will likely have long-term effects on the Bitcoin Ecosystem since they store, transact, and compute more data.
Charges Ordinals introduce scalability challenges. The Bitcoin network has limited transaction throughput and increased fees during peak demand. NFTs could make network transactions harder and more expensive. Ordinals currently occupy over 50% of block space, according to Glassnode.
One of the protocols that supported Ordinals Taproot has also seen a huge uptick:
Taproot use increases block size and transaction costs.
This could cause network congestion but also support more L2s with Ordinals-specific use cases. Dune info here.
Storage Needs The Bitcoin blockchain would need to store more data to store NFT data directly. Since ordinals were introduced, blocksize has tripled from 0.7mb to over 2.2mb, which could increase storage costs and make it harder for nodes to join the network.
Use Case Diversity On the other hand, NFTs on the Bitcoin blockchain could broaden Bitcoin's use cases beyond storage and payment. This could expand Bitcoin's user base. This is two-sided. Bitcoin was designed to be trustless, decentralized, peer-to-peer money.
Chain to permanently store NFTs as ordinals will change everything.
Popularity rise This new use case will boost Bitcoin appeal, according to some. This argument fails since Bitcoin is the most popular cryptocurrency. Popularity doesn't require a new use case. Cryptocurrency adoption boosts Bitcoin. It need not compete with Ethereum or provide extra benefits to crypto investors. If there was a need for another chain that supports NFTs (there isn't), why would anyone choose the slowest and most expensive network? It appears contradictory and unproductive.
Nonetheless, holding an NFT on the Bitcoin blockchain is more secure than any other blockchain, but this has little utility.
Bitcoin NFTs are undoubtedly controversial. NFTs are strange and perhaps harmful to Bitcoin's mission. If Bitcoin NFTs are here to stay, I hope a sidechain or rollup solution will take over and leave the base chain alone.
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Justin Kuepper
3 years ago
Day Trading Introduction
Historically, only large financial institutions, brokerages, and trading houses could actively trade in the stock market. With instant global news dissemination and low commissions, developments such as discount brokerages and online trading have leveled the playing—or should we say trading—field. It's never been easier for retail investors to trade like pros thanks to trading platforms like Robinhood and zero commissions.
Day trading is a lucrative career (as long as you do it properly). But it can be difficult for newbies, especially if they aren't fully prepared with a strategy. Even the most experienced day traders can lose money.
So, how does day trading work?
Day Trading Basics
Day trading is the practice of buying and selling a security on the same trading day. It occurs in all markets, but is most common in forex and stock markets. Day traders are typically well educated and well funded. For small price movements in highly liquid stocks or currencies, they use leverage and short-term trading strategies.
Day traders are tuned into short-term market events. News trading is a popular strategy. Scheduled announcements like economic data, corporate earnings, or interest rates are influenced by market psychology. Markets react when expectations are not met or exceeded, usually with large moves, which can help day traders.
Intraday trading strategies abound. Among these are:
- Scalping: This strategy seeks to profit from minor price changes throughout the day.
- Range trading: To determine buy and sell levels, range traders use support and resistance levels.
- News-based trading exploits the increased volatility around news events.
- High-frequency trading (HFT): The use of sophisticated algorithms to exploit small or short-term market inefficiencies.
A Disputed Practice
Day trading's profit potential is often debated on Wall Street. Scammers have enticed novices by promising huge returns in a short time. Sadly, the notion that trading is a get-rich-quick scheme persists. Some daytrade without knowledge. But some day traders succeed despite—or perhaps because of—the risks.
Day trading is frowned upon by many professional money managers. They claim that the reward rarely outweighs the risk. Those who day trade, however, claim there are profits to be made. Profitable day trading is possible, but it is risky and requires considerable skill. Moreover, economists and financial professionals agree that active trading strategies tend to underperform passive index strategies over time, especially when fees and taxes are factored in.
Day trading is not for everyone and is risky. It also requires a thorough understanding of how markets work and various short-term profit strategies. Though day traders' success stories often get a lot of media attention, keep in mind that most day traders are not wealthy: Many will fail, while others will barely survive. Also, while skill is important, bad luck can sink even the most experienced day trader.
Characteristics of a Day Trader
Experts in the field are typically well-established professional day traders.
They usually have extensive market knowledge. Here are some prerequisites for successful day trading.
Market knowledge and experience
Those who try to day-trade without understanding market fundamentals frequently lose. Day traders should be able to perform technical analysis and read charts. Charts can be misleading if not fully understood. Do your homework and know the ins and outs of the products you trade.
Enough capital
Day traders only use risk capital they can lose. This not only saves them money but also helps them trade without emotion. To profit from intraday price movements, a lot of capital is often required. Most day traders use high levels of leverage in margin accounts, and volatile market swings can trigger large margin calls on short notice.
Strategy
A trader needs a competitive advantage. Swing trading, arbitrage, and trading news are all common day trading strategies. They tweak these strategies until they consistently profit and limit losses.
Strategy Breakdown:
Type | Risk | Reward
Swing Trading | High | High
Arbitrage | Low | Medium
Trading News | Medium | Medium
Mergers/Acquisitions | Medium | High
Discipline
A profitable strategy is useless without discipline. Many day traders lose money because they don't meet their own criteria. “Plan the trade and trade the plan,” they say. Success requires discipline.
Day traders profit from market volatility. For a day trader, a stock's daily movement is appealing. This could be due to an earnings report, investor sentiment, or even general economic or company news.
Day traders also prefer highly liquid stocks because they can change positions without affecting the stock's price. Traders may buy a stock if the price rises. If the price falls, a trader may decide to sell short to profit.
A day trader wants to trade a stock that moves (a lot).
Day Trading for a Living
Professional day traders can be self-employed or employed by a larger institution.
Most day traders work for large firms like hedge funds and banks' proprietary trading desks. These traders benefit from direct counterparty lines, a trading desk, large capital and leverage, and expensive analytical software (among other advantages). By taking advantage of arbitrage and news events, these traders can profit from less risky day trades before individual traders react.
Individual traders often manage other people’s money or simply trade with their own. They rarely have access to a trading desk, but they frequently have strong ties to a brokerage (due to high commissions) and other resources. However, their limited scope prevents them from directly competing with institutional day traders. Not to mention more risks. Individuals typically day trade highly liquid stocks using technical analysis and swing trades, with some leverage.
Day trading necessitates access to some of the most complex financial products and services. Day traders usually need:
Access to a trading desk
Traders who work for large institutions or manage large sums of money usually use this. The trading or dealing desk provides these traders with immediate order execution, which is critical during volatile market conditions. For example, when an acquisition is announced, day traders interested in merger arbitrage can place orders before the rest of the market.
News sources
The majority of day trading opportunities come from news, so being the first to know when something significant happens is critical. It has access to multiple leading newswires, constant news coverage, and software that continuously analyzes news sources for important stories.
Analytical tools
Most day traders rely on expensive trading software. Technical traders and swing traders rely on software more than news. This software's features include:
-
Automatic pattern recognition: It can identify technical indicators like flags and channels, or more complex indicators like Elliott Wave patterns.
-
Genetic and neural applications: These programs use neural networks and genetic algorithms to improve trading systems and make more accurate price predictions.
-
Broker integration: Some of these apps even connect directly to the brokerage, allowing for instant and even automatic trade execution. This reduces trading emotion and improves execution times.
-
Backtesting: This allows traders to look at past performance of a strategy to predict future performance. Remember that past results do not always predict future results.
Together, these tools give traders a competitive advantage. It's easy to see why inexperienced traders lose money without them. A day trader's earnings potential is also affected by the market in which they trade, their capital, and their time commitment.
Day Trading Risks
Day trading can be intimidating for the average investor due to the numerous risks involved. The SEC highlights the following risks of day trading:
Because day traders typically lose money in their first months of trading and many never make profits, they should only risk money they can afford to lose.
Trading is a full-time job that is stressful and costly: Observing dozens of ticker quotes and price fluctuations to spot market trends requires intense concentration. Day traders also spend a lot on commissions, training, and computers.
Day traders heavily rely on borrowing: Day-trading strategies rely on borrowed funds to make profits, which is why many day traders lose everything and end up in debt.
Avoid easy profit promises: Avoid “hot tips” and “expert advice” from day trading newsletters and websites, and be wary of day trading educational seminars and classes.
Should You Day Trade?
As stated previously, day trading as a career can be difficult and demanding.
- First, you must be familiar with the trading world and know your risk tolerance, capital, and goals.
- Day trading also takes a lot of time. You'll need to put in a lot of time if you want to perfect your strategies and make money. Part-time or whenever isn't going to cut it. You must be fully committed.
- If you decide trading is for you, remember to start small. Concentrate on a few stocks rather than jumping into the market blindly. Enlarging your trading strategy can result in big losses.
- Finally, keep your cool and avoid trading emotionally. The more you can do that, the better. Keeping a level head allows you to stay focused and on track.
If you follow these simple rules, you may be on your way to a successful day trading career.
Is Day Trading Illegal?
Day trading is not illegal or unethical, but it is risky. Because most day-trading strategies use margin accounts, day traders risk losing more than they invest and becoming heavily in debt.
How Can Arbitrage Be Used in Day Trading?
Arbitrage is the simultaneous purchase and sale of a security in multiple markets to profit from small price differences. Because arbitrage ensures that any deviation in an asset's price from its fair value is quickly corrected, arbitrage opportunities are rare.
Why Don’t Day Traders Hold Positions Overnight?
Day traders rarely hold overnight positions for several reasons: Overnight trades require more capital because most brokers require higher margin; stocks can gap up or down on overnight news, causing big trading losses; and holding a losing position overnight in the hope of recovering some or all of the losses may be against the trader's core day-trading philosophy.
What Are Day Trader Margin Requirements?
Regulation D requires that a pattern day trader client of a broker-dealer maintain at all times $25,000 in equity in their account.
How Much Buying Power Does Day Trading Have?
Buying power is the total amount of funds an investor has available to trade securities. FINRA rules allow a pattern day trader to trade up to four times their maintenance margin excess as of the previous day's close.
The Verdict
Although controversial, day trading can be a profitable strategy. Day traders, both institutional and retail, keep the markets efficient and liquid. Though day trading is still popular among novice traders, it should be left to those with the necessary skills and resources.

Alex Mathers
3 years ago
8 guidelines to help you achieve your objectives 5x fast
If you waste time every day, even though you're ambitious, you're not alone.
Many of us could use some new time-management strategies, like these:
Focus on the following three.
You're thinking about everything at once.
You're overpowered.
It's mental. We just have what's in front of us. So savor the moment's beauty.
Prioritize 1-3 things.
To be one of the most productive people you and I know, follow these steps.
Get along with boredom.
Many of us grow bored, sweat, and turn on Netflix.
We shout, "I'm rarely bored!" Look at me! I'm happy.
Shut it, Sally.
You're not making wonderful things for the world. Boredom matters.
If you can sit with it for a second, you'll get insight. Boredom? Breathe.
Go blank.
Then watch your creativity grow.
Check your MacroVision once more.
We don't know what to do with our time, which contributes to time-wasting.
Nobody does, either. Jeff Bezos won't hand-deliver that crap to you.
Daily vision checks are required.
Also:
What are 5 things you'd love to create in the next 5 years?
You're soul-searching. It's food.
Return here regularly, and you'll adore the high you get from doing valuable work.
Improve your thinking.
What's Alex's latest nonsense?
I'm talking about overcoming our own thoughts. Worrying wastes so much time.
Too many of us are assaulted by lies, myths, and insecurity.
Stop letting your worries massage you into a worried coma like a Thai woman.
Optimizing your thoughts requires accepting what you can't control.
It means letting go of unhelpful thoughts and returning to the moment.
Keep your blood sugar level.
I gave up gluten, donuts, and sweets.
This has really boosted my energy.
Blood-sugar-spiking carbs make us irritable and tired.
These day-to-day ups and downs aren't productive. It's crucial.
Know how your diet affects insulin levels. Now I have more energy and can do more without clenching my teeth.
Reduce harmful carbs to boost energy.
Create a focused setting for yourself.
When we optimize the mind, we have more energy and use our time better because we're not tense.
Changing our environment can also help us focus. Disabling alerts is one example.
Too hot makes me procrastinate and irritable.
List five items that hinder your productivity.
You may be amazed at how much you may improve by removing distractions.
Be responsible.
Accountability is a time-saver.
Creating an emotional pull to finish things.
Writing down our goals makes us accountable.
We can engage a coach or work with an accountability partner to feel horrible if we don't show up and finish on time.
‘Hey Jake, I’m going to write 1000 words every day for 30 days — you need to make sure I do.’ ‘Sure thing, Nathan, I’ll be making sure you check in daily with me.’
Tick.
You might also blog about your ambitions to show your dedication.
Now you can't hide when you promised to appear.
Acquire a liking for bravery.
Boldness changes everything.
I sometimes feel lazy and wonder why. If my food and sleep are in order, I should assess my footing.
Most of us live backward. Doubtful. Uncertain. Feelings govern us.
Backfooting isn't living. It's lame, and you'll soon melt. Live boldly now.
Be assertive.
Get disgustingly into everything. Expand.
Even if it's hard, stop being a b*tch.
Those that make Mr. Bold Bear their spirit animal benefit. Save time to maximize your effect.

mbvissers.eth
3 years ago
Why does every smart contract seem to implement ERC165?
ERC165 (or EIP-165) is a standard utilized by various open-source smart contracts like Open Zeppelin or Aavegotchi.
What's it? You must implement? Why do we need it? I'll describe the standard and answer any queries.
What is ERC165
ERC165 detects and publishes smart contract interfaces. Meaning? It standardizes how interfaces are recognized, how to detect if they implement ERC165, and how a contract publishes the interfaces it implements. How does it work?
Why use ERC165? Sometimes it's useful to know which interfaces a contract implements, and which version.
Identifying interfaces
An interface function's selector. This verifies an ABI function. XORing all function selectors defines an interface in this standard. The following code demonstrates.
// SPDX-License-Identifier: UNLICENCED
pragma solidity >=0.8.0 <0.9.0;
interface Solidity101 {
function hello() external pure;
function world(int) external pure;
}
contract Selector {
function calculateSelector() public pure returns (bytes4) {
Solidity101 i;
return i.hello.selector ^ i.world.selector;
// Returns 0xc6be8b58
}
function getHelloSelector() public pure returns (bytes4) {
Solidity101 i;
return i.hello.selector;
// Returns 0x19ff1d21
}
function getWorldSelector() public pure returns (bytes4) {
Solidity101 i;
return i.world.selector;
// Returns 0xdf419679
}
}This code isn't necessary to understand function selectors and how an interface's selector can be determined from the functions it implements.
Run that sample in Remix to see how interface function modifications affect contract function output.
Contracts publish their implemented interfaces.
We can identify interfaces. Now we must disclose the interfaces we're implementing. First, import IERC165 like so.
pragma solidity ^0.4.20;
interface ERC165 {
/// @notice Query if a contract implements an interface
/// @param interfaceID The interface identifier, as specified in ERC-165
/// @dev Interface identification is specified in ERC-165.
/// @return `true` if the contract implements `interfaceID` and
/// `interfaceID` is not 0xffffffff, `false` otherwise
function supportsInterface(bytes4 interfaceID) external view returns (bool);
}We still need to build this interface in our smart contract. ERC721 from OpenZeppelin is a good example.
// SPDX-License-Identifier: MIT
// OpenZeppelin Contracts (last updated v4.5.0) (token/ERC721/ERC721.sol)
pragma solidity ^0.8.0;
import "./IERC721.sol";
import "./extensions/IERC721Metadata.sol";
import "../../utils/introspection/ERC165.sol";
// ...
contract ERC721 is Context, ERC165, IERC721, IERC721Metadata {
// ...
function supportsInterface(bytes4 interfaceId) public view virtual override(ERC165, IERC165) returns (bool) {
return
interfaceId == type(IERC721).interfaceId ||
interfaceId == type(IERC721Metadata).interfaceId ||
super.supportsInterface(interfaceId);
}
// ...
}I deleted unnecessary code. The smart contract imports ERC165, IERC721 and IERC721Metadata. The is keyword at smart contract declaration implements all three.
Kind (interface).
Note that type(interface).interfaceId returns the same as the interface selector.
We override supportsInterface in the smart contract to return a boolean that checks if interfaceId is the same as one of the implemented contracts.
Super.supportsInterface() calls ERC165 code. Checks if interfaceId is IERC165.
function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
return interfaceId == type(IERC165).interfaceId;
}So, if we run supportsInterface with an interfaceId, our contract function returns true if it's implemented and false otherwise. True for IERC721, IERC721Metadata, andIERC165.
Conclusion
I hope this post has helped you understand and use ERC165 and why it's employed.
Have a great day, thanks for reading!
