Creating a Crowdsourcing Smart Contract with Solidity

The fundme contract enables decentralized crowdfunding, allowing users to contribute cryptocurrency for project funding.

### Building a Crowdfunding Smart Contract with Remix and Solidity
* 👋 Welcome to Lesson Four, where we will focus on creating a crowdfunding application using smart contracts, specifically a file named **fundme.sol** and another called **priceconverter.sol**.
* 💡 The fundme contract will function as a **decentralized Kickstarter**, allowing users to contribute cryptocurrencies like **Ethereum, Polygon, and Avalanche** to support projects.
* 💰 Users will be required to send a **minimum of five dollars worth of cryptocurrency** to fund the contract, ensuring that contributions are **meaningful**.
* 🔴 A new red button will appear in the user interface to indicate the fund function, which is **payable and allows for the transfer of native blockchain currency**.
* 🔍 After deploying the contract to a test net, users can send transactions, and upon completion, they will see the **updated balance in etherscan** reflecting their contributions.
* 💸 The contract owner, who is also the user, will have the ability to **withdraw funds**, which will then **return to their wallet** after a successful transaction.
* 📚 As we progress through this section, you'll learn most of the **fundamental concepts of Solidity**, with **advanced features** to be covered later in the course.
* 🤔 If any concepts are unclear, jot down your questions and utilize the **GitHub discussions** or **web3education.dev** for assistance from fellow developers.

All right everybody, welcome back. We are now headed into Lesson Four. This is going to be our remix fund me, and once again, you can find all the code associated with this lesson in the GitHub repository associated with this course and also web3dev.education. And let's do a quick

walkthrough of these contracts before we actually start coding anything to see what we're going to be doing. We're going to be creating one contract fundme.sol. We're also going to have another file called priceconverter.sol, and we'll talk about that in a little bit. The fund

me contract is going to be our main contract. This is going to be an example of a crowdsourcing application or a way to raise money. You can think of it as a web 3 decentralized Kickstarter. We'll allow users to send Ethereum, Polygon, Avalanche, etc., or really any native

blockchain cryptocurrency into this contract and allow the owner of the contract to actually withdraw all the funds for them to go spend on their new project. And we are going to actually deploy this contract to a test net. And remember, use the test net transactions sparingly, but if we deploy this to a

test net, we scroll down, we actually see that we have a couple of buttons and a new color button. We'll actually get a new red button for our fund function. A red button indicates that a function is payable and we can send native Ethereum or Polygon or Avalanche or whatever the

native cryptocurrency of the blockchain we're working with is. We additionally will indicate a minimum USD amount to send to the contract, so funders have to spend at least five dollars worth of Ethereum in order to call this fund contract. So if we go up to the value section, we can actually

send some value with this transaction and again don't worry about this making sense yet but if I want to send 0.01 ether I'll grab that amount in way paste it into the value section here I'll scroll down I'll hit the fund button

minims will pop up I'll confirm we can see at the top the current balance of the contract is zero and we'll wait a little bit for the transaction to finish going through and after the transaction finishes going through we can see in etherscan we have a balance of 0.01 ETH

and we can also see that after remix after a slight delay then we can allow the owner of the contract to withdraw those funds right now the owner of the contract is also us and after this transaction goes through we'll see that balance removed from the contract and

it'll go back into our wallet and as you just saw there if we held our metamask up for long enough eventually it would pop back into our metamask are you excited we should be because after you complete this section you'll actually know most of the fundamentals of working

with solidity we're going to be going over a lot of advanced features in this section and I'll let you know the specific parts that you don't need to fully understand quite yet there's going to be a couple parts where if it doesn't totally make sense just

keep going with the course and as we get later into the course you'll figure out why they make sense but it might be a good idea to write down the questions that you have to ask either an AI on the GitHub discussions or web3education.dev

make sure of course to use the Discussions tab in the Foundry full course F23 to ask questions and interact with other developers who are taking the same course or go to web3dev.education to learn more, alright let's get froggy

Lesson 4 Part 1 | Remix Fund Me - Solidity & Foundry Full Course

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Lesson Four Overview: Remix FundMe Contract

Introduction to Lesson Four: Remix FundMe contract and code location.

Description of the two contracts: fundme.sol (main contract) and priceconverter.sol.

FundMe contract as a decentralized crowdsourcing application, similar to Kickstarter.

Deployment to a testnet and cautious use of testnet transactions.

FundMe Contract Functionality and User Interaction

Visual representation of payable functions with red buttons in Remix.

Minimum USD amount requirement for funding (e.g., $5).

Example transaction: sending 0.01 ETH using the fund button.

Verification of transaction on Etherscan and Remix, showing balance update.

Owner withdrawing funds, demonstrating the process.

Completion of this section covers Solidity fundamentals.

Advanced features will be covered later in the course.

Guidance on asking questions via AI, GitHub discussions, or web3education.dev.

Encouragement to continue learning and engage with the community.