Smart Contract Tutorial - Vending Machine Smart Contract in Solidity 

Thanks for sharing! Just started learning and found your video very helpful

Definitely feel I am absorbing more here than most other videos I’ve seen. Appreciate your efforts and seeing your mistakes helps me see how to problem solve a solution. It’s common for us all. Thanks happy subbed

By far the best tutorial I ever watch on the topic. What a joy, when you understand things and can interact with the program you just built. I started my journey in smart contract development just few months ago and I was overwhelmed by all the other tutos I followed before. Yours are easy to follow along and practical. Thanks a lot for the inspiration. I will not give up on this path, thanks to you. You made me realize that it is doable.

30:20 the problem wasn't for gas fee or etc, it was a problem of remix IDE, you paste the value wei but while you scroll, value becomes zero for a UI bug.

Thank you for the videos so well designed. Do not worry about the mistakes that help us understand much more than if everything is perfect.

Hii, I found error in contract. In line 23.... msg.value is >= amount * 2 ether..... Let say if u pay 50 ether and request 5 donuts.. it will give you 5 donuts without error but u have given 50 ethers. So to avoid this mistake....Refer below code.... Line 23---- msg.value is == amount * 2 ether........just replace > with = By the way, nice tutorial....

The problem was simply ( the value in the box was resetting to zero when you scrolled ) - it wasn't gas-related. You could have also selected ether and put 4 for value. Thank you for the insightful tutorials, l will check out more of your videos.

This is the best tutorial on blockchain uptill now. I just have a problem. I have developed my own erc20 token and i want my lottery contract to send and receive my token instead of ether please tell me how to do it. I need help on this

I have been hitting your videos lol.. most blockchain tutorials doesnt start from scratch but you do. Absolute gem. Thanks man

This was a great video for solidity learners. I have been all over RU-vid for practice projects and this was one of my favorites...great job!

Excellent video. Made learning of smart contracts so easy. Your videos spoon feed us. Keep it up. Your way of teaching is way too cool.

Super nice tutorial! Love that we so easy can play around on the Remix website without downloading, installing, debuging why the installation doesnt work etc

I'm starting with solidity and I still don't have the concepts very clear, so I don't know if the question is silly, but where does the ether that is sent when you buy a donut go? Because I see that the balance of the owner's account does not change

dem donut must be rly friggin good

Tank you for this! I've been following your tutorials, you explain things very well. Hopefully I can make my own mature project some day.

Can't believe you left your address in this video.

amazing tutorial can you make videos on basics of block chain like gas fee and architecture

Should set an maximum number uint for restock , i did not try to call other contract and write 10 trillions donut available :)

It's incredible to see that people like you put this kind of knowledge on RU-vid for free. It's great for the space and people that are at the beginning of their web3 journey.

My transactions have been pending for 10 minutes now. is this normal ?

What is the point of creating a mapping? One can store a simple variable instead of mapping, can't one?

Talking about the purchase function, you tested using the same address as the owner address (msg.sender == owner), how come it worked storing the correct amount of donuts? Could you explain this? I expected something like: donutBalances[0x123] -= 1; donutBalances[0x123] += 1; So the donutBalance of 0x123 would be 100, not 1 or 99.

Bro, you gave me a good night. I enjoyed the video. Thanks a lot.👌

One of the best solidity video out there ! Thanks

I do have a question. So, if an attacker wanted to disrupt this vending machine smart contract, would he or she be able to do so with the parameters you currently have set in place? I've been really studying your most recent videos on smart contract security and I want to learn as much as I can on how to prevent any attacks on the smart contracts I will develop/create in the future. Thank you, in advance, for your guidance.

just subscribed to your channel - your content is good and thank you for the practical examples. However, I have no coding experience and I was just about to buy a Python tutorial, would that help? thanks again

thank you so much for you i am able to complete my college project

30:14 When purchasing donuts, you don't have to account for gas fees in msg.value. They will get added on top of that automatically. The number you have inserted into the value column just kept disappearing without you noticing.

I do have a question. In few last lines you defined how can someone send a transaction, however, I didn't see you specified anywhere whom the receiver should be. Is that a mistake or I missed something? Also I saw balance of your acc was 95.99ether and you used it from the same account so it should have been 99.99 (because those 4 eth would come to your address anyways)

the architecture overview made everything come together, great work!

Hi, this indeed is a great, great video. I have learned quite a lot from it. However, the only missing link for me is that, I see two balances, which are the donut balances and the contract balance. You have very clearly shown how to work with the donut balances but I am still clueless as to how to work with contract balance. How can I see/view how much is the contract balance? How can I use it in the contract. For instance, my understanding is that in the real world, I also need to spend some eth to restock, and I must spend the eth I received from sales (this is excluding gas fees I pay to blockchain I guess). But otherwise thank you, this is indeed a great tutorial.

You enter the wei value on the remix ide and you make the purchase, but when I make the purchase with truffle and ganazhe, I get the error 'You must pay at least 2 ether per donut', what should I do here?

Your videos are explanatory I’m following all your tutorials to write smart contract code for my publication.

What is the use of , address (this) and why we use this

Coming from a desktop apps background, my biggest challenge is adapting to the blockchain paradigm but the length of the tutorials (just right) and teaching style set off little light bulbs in my head. Thanks!

Hi! It is a nice tutorial, but needs an important function: withdraw. Otherwise the money will stay in the contract forever and there is no way to get the funds!

Wow! Wow! Woowow! Just wow! This is my second tutorial from you channel and you are so damn good in it I love the way you explain stuff... I owe you a thanks in person 🌍

My only question is, how do we put a cap on the amount of donuts to restock? you could add them infinitely.

simple but worthy watch. I am learnign solidity rn and this helped me learn a lot.

thx man, great video you deliver the content in such a way that makes it so clear to understand

without a doubt the best videos for solidity. Tysm, I hope more videos are on their way

good video, could the vending machine sell an erc20 or erc 721 token?

Can we send a notification to the owner to check if they want to restock or not (before automatic restocking)?

30:00 you don't need to send more than 4 eth to buy the 2 donuts. each excess eth sent will be lost. the gas fee is separated

Please keeping making more. Great video 🔥🔥

thanks again Jonathan! great job!

Thank you for this amazing vedio , but regarding purchase fucntion , should we use (send or transfer function) to transfer msg.value to the Owner ? , please advise

Just awesome, lucid to understand...👍👍👍

Great Job! I learned a lot, really helpful

We need more examples like this thanku

Thanks for this video Block Explorer. I noticed a slight issue though, if the value passed is let's say 20 ether and the purchased donuts are just 8 ( which should cost 16 ether ) it still deducts 20 ether from the balance. How can we fix this?

Very new to this - great tutorial! Just one basic question - when payments are sent along with a function invocation on a smart contract, does that value go to the owner? I assumed yes but just wanted to clarify

Best tutorial Don't worry we got it.

thanks a lot bro for all these video

thanks

please do a flash loan course

Thank you for sharing!

This was a great video to see how to make a smart contract. One thing I wanted to learn more about was, in this contract, how to make it work with Value and Purchase QTY. So in my code I priced the Product at .0001 ether. I paid 2 Ether (msg.value) but asked to purchase 2 products. I see the vending machine deducted the 2 (down to 98) but the ether I paid was used to buy the product, but the extra is just lost. Where is it?

where's my donut

First!

Is that a typo? : Vending Machine Smart Cuntract in Solidity C u n t r a c t ? 🤣🤣🤣🤣🤣