Note

For lesson 4 Code, switch to L4 branch 🌿

Deployments

ZkSync - 0xc3290b06957b9A75AA1EF4a99307DFB72faE6B01

ZkSync testnet - 0x0729ABD1CD5d7BfE08F2d8Ce87c4C2cDD5FC7656

Base - 0xddfEcC36670F8F3f875587f37E4982527E9410C4

Base Sepolia - 0xddfEcC36670F8F3f875587f37E4982527E9410C4

Sepolia testnet - 0xA5cAC1cC06D664A2E778C0192BAb6D2ebf989719

Directions for use

To play around with this code locally run the following commands in your local terminal in order:

git clone https://github.com/SimSimButDifferent/L3-L4-EthWallet.git
yarn

Then split the terminal and run the below code in the other half:

yarn hardhat node

Finally, deploy to the hardhat node using:

yarn hardhat run scripts/deploy.js --network localhost

Lesson 3: Functions and Modifiers in Solidity

Objective:

To understand how to write and use functions in Solidity, and to learn about function modifiers for enforcing certain conditions and managing access control in smart contracts.

Part 1: Functions in Solidity

Function Declaration and Types:

Understand the syntax for declaring functions. Different types of functions: public, private, internal, and external.

Return Values and Visibility:

How to define return values for functions. Understand the implications of function visibility.

Function Modifiers:

Usage of view, pure, and state-changing functions.

Function Parameters:

Passing parameters to functions. Using memory and storage keywords for complex data types.

Example: Creating a Function

solidity Copy code pragma solidity ^0.8.0;

contract MyContract { uint public count = 0;

function increment() public {
    count += 1;
}

function getCount() public view returns (uint) {
    return count;
}

}

Part 2: Modifiers in Solidity

Understanding Modifiers:

Purpose of modifiers in Solidity. Writing custom modifiers to enforce conditions. Common Use Cases:

Restricting access to certain functions. Validating inputs or conditions before executing function logic. Example: Using a Modifier

solidity Copy code pragma solidity ^0.8.0;

contract MyContract { address public owner;

constructor() {
    owner = msg.sender;
}

modifier onlyOwner() {
    require(msg.sender == owner, "Not the owner");
    _;
}

function changeOwner(address newOwner) public onlyOwner {
    owner = newOwner;
}

}

Assignments and Practical Exercises

Assignment 1:

Research and write a brief explanation of how and why view and pure modifiers are used in Solidity functions.

Exercise 1:

Create a smart contract with a few functions demonstrating different visibility levels (public, private, internal, external) and return values.

Exercise 2:

Write a contract that includes a custom modifier. Use this modifier to restrict access to one of the contract's functions.

Token Wallet with Withdrawal Limits

Use Case Overview: Implement a smart contract that acts as a wallet for a specific token. This contract would allow users to deposit, withdraw, and check their token balance, with daily withdrawal limits for security.

Functions:

depositTokens: A public function to deposit tokens into the wallet. withdrawTokens: An external function to withdraw a specified amount of tokens, adhering to daily limits. getBalance: A public view function to check the token balance of a user. Modifiers:

withdrawalLimitCheck: A custom modifier to enforce the daily withdrawal limit per user. sufficientBalance: A modifier to ensure the user has enough tokens for withdrawal requests. These use cases involve various function types and custom modifiers, providing a comprehensive understanding of how these elements can be combined to build functional and secure smart contracts. You can further explore these ideas by considering aspects like security, efficiency, and user interaction within the smart contract ecosystem.

This lesson will help you understand how to structure the logic within your smart contracts using functions and modifiers. These are key concepts in Solidity and are essential for writing secure and efficient smart contracts. Once you've completed this lesson, you'll have a deeper understanding of how to control access and enforce specific logic flows in your smart contracts.