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!

Price Intelligently put out amazing content on pricing your SaaS product. This blog's link to the whole report is worth reading. Our key takeaways are below.

Don't base prices on the competition. Competitor-based pricing has clear drawbacks. Their pricing approach is yours. Your company offers customers something unique. Otherwise, you wouldn't create it. This strategy is static, therefore you can't add value by raising prices without outpricing competitors. Look, but don't touch is the competitor-based moral. You want to know your competitors' prices so you're in the same ballpark, but they shouldn't guide your selections. Competitor-based pricing also drives down prices.

Value-based pricing wins. This is customer-based pricing. Value-based pricing looks outward, not inward or laterally at competitors. Your clients are the best source of pricing information. By valuing customer comments, you're focusing on buyers. They'll decide if your pricing and packaging are right. In addition to asking consumers about cost savings or revenue increases, look at data like number of users, usage per user, etc.

Value-based pricing increases prices. As you learn more about the client and your worth, you'll know when and how much to boost rates. Every 6 months, examine pricing.

Cloning top customers. You clone your consumers by learning as much as you can about them and then reaching out to comparable people or organizations. You can't accomplish this without knowing your customers. Segmenting and reproducing them requires as much detail as feasible. Offer pricing plans and feature packages for 4 personas. The top plan should state Contact Us. Your highest-value customers want more advice and support.

Question your 4 personas. What's the one item you can't live without? Which integrations matter most? Do you do analytics? Is support important or does your company self-solve? What's too cheap? What's too expensive?

Not everyone likes per-user pricing. SaaS organizations often default to per-user analytics. About 80% of companies utilizing per-user pricing should use an alternative value metric because their goods don't give more value with more users, so charging for them doesn't make sense.

At least 3:1 LTV/CAC. Break even on the customer within 2 years, and LTV to CAC is greater than 3:1. Because customer acquisition costs are paid upfront but SaaS revenues accrue over time, SaaS companies face an early financial shortfall while paying back the CAC.

ROI should be >20:1. Indeed. Ensure the customer's ROI is 20x the product's cost. Microsoft Office costs $80 a year, but consumers would pay much more to maintain it.

A/B Testing. A/B testing is guessing. When your pricing page varies based on assumptions, you'll upset customers. You don't have enough customers anyway. A/B testing optimizes landing pages, design decisions, and other site features when you know the problem but not pricing.

Don't discount. It cheapens the product, makes it permanent, and increases churn. By discounting, you're ruining your pricing analysis.

"Don't let technology control you; manage your phone."

"Don't become a slave to technology," said Richard Branson. "Manage your phone, don't let it manage you."

Unfortunately, most people are addicted to smartphones.

Worrying smartphone statistics:

• 46% of smartphone users spend 5–6 hours daily on their device.

• The average adult spends 3 hours 54 minutes per day on mobile devices.

• We check our phones 150–344 times per day (every 4 minutes).

• During the pandemic, children's daily smartphone use doubled.

Having a list of productive, healthy, and fulfilling replacement activities is an effective way to reduce smartphone use.

The more you practice these smartphone replacements, the less time you'll waste.

Skills Development

Most people say they 'don't have time' to learn new skills or read more. Lazy justification. The issue isn't time, but time management. Distractions and low-quality entertainment waste hours every day.

The majority of time is spent in low-quality ways, according to Richard Koch, author of The 80/20 Principle.

What if you swapped daily phone scrolling for skill-building?

There are dozens of skills to learn, from high-value skills to make more money to new languages and party tricks.

Learning a new skill will last for years, if not a lifetime, compared to scrolling through your phone.

Watch Docs

Love documentaries. It's educational and relaxing. A good documentary helps you understand the world, broadens your mind, and inspires you to change.

Recent documentaries I liked include:

• 14 Peaks: Nothing Is Impossible

• The Social Dilemma

• Jim & Andy: The Great Beyond

• Fantastic Fungi

Make money online

If you've ever complained about not earning enough money, put away your phone and get to work.

Instead of passively consuming mobile content, start creating it. Create something worthwhile. Freelance.

Internet makes starting a business or earning extra money easier than ever.

(Grand)parents didn't have this. Someone made them work 40+ hours. Few alternatives existed.

Today, all you need is internet and a monetizable skill. Use the internet instead of letting it distract you. Profit from it.

Bookworm

Jack Canfield, author of Chicken Soup For The Soul, said, "Everyone spends 2–3 hours a day watching TV." If you read that much, you'll be in the top 1% of your field."

Few people have more than two hours per day to read.

If you read 15 pages daily, you'd finish 27 books a year (as the average non-fiction book is about 200 pages).

Jack Canfield's quote remains relevant even though 15 pages can be read in 20–30 minutes per day. Most spend this time watching TV or on their phones.

What if you swapped 20 minutes of mindless scrolling for reading? You'd gain knowledge and skills.

Favorite books include:

• The 7 Habits of Highly Effective People — Stephen R. Covey

• The War of Art — Steven Pressfield

• The Psychology of Money — Morgan Housel

• A New Earth — Eckart Tolle

Get Organized

All that screen time could've been spent organizing. It could have been used to clean, cook, or plan your week.

If you're always 'behind,' spend 15 minutes less on your phone to get organized.

"Give me six hours to chop down a tree, and I'll spend the first four sharpening the ax," said Abraham Lincoln. Getting organized is like sharpening an ax, making each day more efficient.

Creativity

Why not be creative instead of consuming others'? Do something creative, like:

• Painting

• Musically

• Photography\sWriting

• Do-it-yourself

• Construction/repair

Creative projects boost happiness, cognitive functioning, and reduce stress and anxiety. Creative pursuits induce a flow state, a powerful mental state.

This contrasts with smartphones' effects. Heavy smartphone use correlates with stress, depression, and anxiety.

Hike

People spend 90% of their time indoors, according to research. This generation is the 'Indoor Generation'

We lack an active lifestyle, fresh air, and vitamin D3 due to our indoor lifestyle (generated through direct sunlight exposure). Mental and physical health issues result.

Put away your phone and get outside. Go on nature walks. Explore your city on foot (or by bike, as we do in Amsterdam) if you live in a city. Move around! Outdoors!

You can't spend your whole life staring at screens.

Podcasting

Okay, a smartphone is needed to listen to podcasts. When you use your phone to get smarter, you're more productive than 95% of people.

Favorite podcasts:

• The Pomp Podcast (about cryptocurrencies)

• The Joe Rogan Experience

• Kwik Brain (by Jim Kwik)

Podcasts can be enjoyed while walking, cleaning, or doing laundry. Win-win.

Journalize

I find journaling helpful for mental clarity. Writing helps organize thoughts.

Instead of reading internet opinions, comments, and discussions, look inward. Instead of Twitter or TikTok, look inward.

“It never ceases to amaze me: we all love ourselves more than other people, but care more about their opinion than our own.” — Marcus Aurelius

Give your mind free reign with pen and paper. It will highlight important thoughts, emotions, or ideas.

Never write for another person. You want unfiltered writing. So you get the best ideas.

Find your best hobbies

List your best hobbies. I guarantee 95% of people won't list smartphone scrolling.

It's often low-quality entertainment. The dopamine spike is short-lived, and it leaves us feeling emotionally 'empty'

High-quality leisure sparks happiness. They make us happy and alive. Everyone has different interests, so these activities vary.

My favorite quality hobbies are:

• Nature walks (especially the mountains)

• Video game party

• Watching a film with my girlfriend

• Gym weightlifting

• Complexity learning (such as the blockchain and the universe)

This brings me joy. They make me feel more fulfilled and 'rich' than social media scrolling.

Make a list of your best hobbies to refer to when you're spending too much time on your phone.

Here’s why that’s baloney

Mark Cuban popularized entrepreneurship.

Shark Tank (which made Mark famous) made starting a business glamorous to attract more entrepreneurs. First off

This isn't an anti-billionaire rant.

Mark Cuban has done excellent. He's a smart, principled businessman. I enjoy his Web3 work. But Mark's work and productivity theories are absurd.

You don't need to outwork everyone in this recession to live well.

You won't be able to outwork me.

Yuck! Mark's words made me gag.

Why do boys think working is a football game where the winner wins a Super Bowl trophy? To outwork you.

Hard work doesn't equal intelligence.

Highly clever professionals spend 4 hours a day in a flow state, then go home to relax with family.

If you don't put forth the effort, someone else will.

- Mark.

He'll burn out. He's delusional and doesn't understand productivity. Boredom or disconnection spark our best thoughts.

TikTok outlaws boredom.

In a spare minute, we check our phones because we can't stand stillness.

All this work p*rn makes things worse. When is it okay to feel again? Because I can’t feel anything when I’m drowning in work and haven’t had a holiday in 2 years.

Your rivals are actively attempting to undermine you.

Ohhh please Mark…seriously.

This isn't a Tom Hanks war film. Relax. Not everyone is a rival. Only yourself is your competitor. To survive the recession, be better than a year ago.

If you get rich, great. If not, there's more to life than Lambos and angel investments.

Some want to relax and enjoy life. No competition. We witness people with lives trying to endure the recession and record-high prices.

This fictitious rival worsens life and work.

If you are truly talented, you will motivate others to work more diligently and effectively.

No Mark. Soz.

If you're a good leader, you won't brag about working hard and treating others like cogs. Treat them like humans. You'll have EQ.

Silly statements like this are caused by an out-of-control ego. No longer watch Shark Tank.

Ego over humanity.

Good leaders will urge people to keep together during the recession. Good leaders support those who are laid off and need a reference.

Not harder, quicker, better. That created my mental health problems 10 years ago.

Truth: we want to work less.

The promotion of entrepreneurship is ludicrous.

Marvel superheroes. Seriously, relax Max.

I used to write about entrepreneurship, then I quit. Many WeWork Adam Neumanns. Carelessness.

I now utilize the side hustle title when writing about online company or entrepreneurship. Humanizes.

Stop glorifying. Thinking we'll all be Elon Musks who send rockets to Mars is delusional. Most of us won't create companies employing hundreds.

OK.

The true epidemic is glorification. fewer selfies Little birdy needs less bank account screenshots. Less Uber talk.

We're exhausted.

Fun, ego-free business can transform the world. Take a relax pill.

Work as if someone were attempting to take everything from you.

I've seen people lose everything.

Myself included. My 20s startup failed. I was almost bankrupt. I thought I'd never recover. Nope.

Best thing ever.

Losing everything reveals your true self. Unintelligent entrepreneur egos perish instantly. Regaining humility revitalizes relationships.

Money's significance shifts. Stop chasing it like a puppy with a bone.

Fearing loss is unfounded.

Here is a more effective approach than outworking nobody.

(You'll thrive in the recession and become wealthy.)

Smarter work

Overworking is donkey work.

You don't want to be a career-long overworker. Instead than wasting time, write down what you do. List tasks and processes.

Keep doing/outsource the list. Step-by-step each task. Continuously systematize.

Then recruit a digital employee like Zapier or a virtual assistant in the same country.

Intelligent, not difficult.

If your big break could burn in hell, diversify like it will.

People err by focusing on one chance.

Chances can vanish. All-in risky. Instead of working like a Mark Cuban groupie, diversify your income.

If you're employed, your customer is your employer.

Sell the same abilities twice and add 2-3 contract clients. Reduce your hours at your main job and take on more clients.

Leave brand loyalty behind

Mark desires his employees' worship.

That's stupid. When times are bad, layoffs multiply. The problem is the false belief that companies care. No. A business maximizes profit and pays you the least.

To care or overpay is anti-capitalist (that run the world). Be honest.

I was a banker. Then the bat virus hit and jobs disappeared faster than I urinate after a night of drinking.

Start being disloyal now since your company will cheerfully replace you with a better applicant. Meet recruiters and hiring managers on LinkedIn. Whenever something goes wrong at work, act.

Loyalty to self and family. Nobody.

Outwork this instead

Mark doesn't suggest outworking inflation instead of people.

Inflation erodes your time on earth. If you ignore inflation, you'll work harder for less pay every minute.

Financial literacy beats inflation.

Get a side job and earn money online

So you can stop outworking everyone.

Internet leverages time. Same effort today yields exponential results later. There are still whole places not online.

Instead of working forever, generate money online.

Final Words

Overworking is stupid. Don't listen to wealthy football jocks.

Work isn't everything. Prioritize diversification, internet income streams, boredom, and financial knowledge throughout the recession.

That’s how to get wealthy rather than burnout-rich.