CSCE-5575-HW-2-Template
Instructor: Beddhu Murali

Second Homework template for blockchain course CSCE 4575/5575

Introduction

In this homework, you will be using smart contracts provided by other parties in your smart contract. Think it as using libraries in programming languages such as Java or C++.

The contract you will be using is Ownable.sol by OpenZeppelin. More info will be in the following section.

The goal of the homework is to design a contract with some functionalities only accessible/callable by the owner of the contract. You will also learn about payment to and from the smart contract.

Tasks

Chain-end

Develop a smart contract with the "Lorem, ipsum, dolor, sit, amet, consectetur, adipiscing, elit, sed, do" array. Similar to the previous assignments, you will have a number variable, which will be used to control how the array gets sliced.

The contract will be "Ownable". Look up how inheritance works in Solidity.

This time, you will have two functions to get slice of array:

firstNumElements
- Returns the elements from the first index, up until 'num' variable
lastNumElements
- Returns theh elements starting from the 'num' index up until the end of the array

These functions will be payable. "firstNumElements" will require the user to pay "0.001" and "lastNumElements", "0.002".

There will be a function to update the number similar to the previous assignments, however, this function will be only callable by the owner/creator of the contract only.

Finally, there will be a function to transfer all the funds from the contract to the owner of the contract. This function will also be callable only by the contract owner.

Front-end

You will display the address of the owner of the contract
Similar to previous assignment, your address and ETH balance
Display the num value and the array slice
Necessary buttons to perform the function calls
Necessary input fields to use set number function

Include any other necessary functions to perform the tasks.

Environment Setup

Run the setup.sh script.

Add import "@openzeppelin/contracts/access/Ownable.sol" to your Counter.sol file.

Any other dependencies should be installed by the script.

Sources

Ownable: https://docs.openzeppelin.com/contracts/4.x/access-control
Payable:
- https://docs.alchemy.com/docs/solidity-payable-functions
- https://solidity-by-example.org/payable/
Receive and Fallback functions
- https://solidity-by-example.org/fallback/
- https://ethereum.stackexchange.com/questions/81994/what-is-the-receive-keyword-in-solidity
Payable functions emit events:
- https://solidity-by-example.org/events/
- https://www.tutorialspoint.com/solidity/solidity_events.htm

Helper Functions

Due to a recent change in OppenZeppelin's Ownable.sol's code, you have to initialize your constructor as follows:

// We don't need to define an address variable for owner.
// Ownable does this for us and you can get the value by calling the "owner" function.

constructor(address initialOwner) Ownable(initialOwner) {
  // Other initializations here
}

Since our constructor now has arguments, to create a smart contract using Foundry, you must use the following command:

# Use the same account's address and private key
forge create --rpc-url http://127.0.0.1:8545 --private-key <private_key> src/Counter.sol:Counter --constructor-args <deployer_account_address>

In order to send ETH to the functions that require it using Foundry, you can use this:

cast call <contract_address> "your_function()" --private-key <private_key> --value 0.001ether  # Or any other ether value

ArmanHZ/CSCE-5575-HW-2-Template

CSCE-5575-HW-2-Template Instructor: Beddhu Murali