4.10 Twitter Dapp 01 Smart Contract

source from "design.tutsplus.com"

Overview

1. Create a Twitter Contract (ep.7) 🌳
2. Creat a mapping between user and tweet 🌳
3. Add function to creat a tweet and save it in mapping 🌳
4. Create a function to get Tweet (ep.11) 🌳
5. Define a Tweet Struct with Author, content, timestamp, likes (ep.13) 🌳
6. Add the struct to array Test tweets (ep.13) 🌳
7. Use require to limit the length of the tweet to be only 280 characters (ep.15) 🌳
8. Add a function called change TweetLength to change max tweet length ( Hint: use newTweetLength as input for function) (ep.17) 🌳
9. Create a constructor function to set an owner of contract (ep.17) 🌳
10. Create a modifier called onlyOwner (ep.17) 🌳
11. Use onlyOwner on the changeTweetLength function (ep.17) 🌳
12. Add id to Tweet Struct to make every Tweet Unique (ep.18)🌳
13. Set the id to be the Tweet [ ] length (Hint: you do it in the creatTweet function) ep.18)🌳
14. Add a function to like the tweet (Hint: there should be 2 paramenters, id and author ep.18) 🌳
15. Add a function to unlike the tweet (make sure you can unlike only if likes count is greater than 0 (ep.18) 🌳
16. Mark both functions external (ep.18) 🌳
17. Deploy Smart Contract to Sepolia (ep.19) 🌳
18. Create Event for creating the tweet, called TweetCreated (Use parameters like id, author, content, timestamp) (ep.21)🌳
19. Emit the event in the createTweet() function below(ep.21)🌳
20. Create Event for liking the tweet, called TweetLiked (Use parameters like liker, tweetAuthor, tweetId, newLikeCount(ep.21)🌳
21. Emit the event in the likeTweet() function below(ep.21)🌳
22. Create a function, getTotalLikes, get total Tweet likes for the user ( User parameters of author) (ep.24) 🌳
23. Loop over all the tweets (ep.24) 🌳
24. sum up totalLikes (ep.24) 🌳
25. Return totalLike (ep.24) 🌳
26. Save UserProfile to the mapping in the setProfile() function// HINT: don't forget to set the _displayName and _bio (ep.28)
27. // 2️⃣ Add a getProfile() function to the interface ✅//
28. 3️⃣ Initialize the IProfile in the contructor ✅// HINT: don't forget to include the _profileContract address as a input//
29. 4️⃣ Create a modifier called onlyRegistered that require the msg.sender to have a profile ✅// HINT: use the getProfile() to get the user// HINT: check if displayName.length > 0 to make sure the user exists//
30. 5️⃣ ADD the onlyRegistered modified to createTweet, likeTweet, and unlikeTweet function ✅

// SPDX-License-Identifier: MIT
pragma solidity ^ 0.8.24;

contract Twitter { // 1️⃣ Create a Twitter Contract
// 定義不可改變的數字
uint16 public MAX_TWEET_LENGTH = 280;  
 
// 5️⃣ Define a Tweet Struct with Author, content, timestamp, likes
// Struct: define a tweet wtih multiple data
// 1️⃣1️⃣ Add id to Tweet Struct to make every Tweet Unique 
    struct Tweet {
        uint256 id;
        address author;
        string content;
        uint256 timestamp;
        uint256 likes;
    }

// 2️⃣ Create a mappping between user and tweet 
    mapping(address => Tweet[] ) public tweets; 
    address public owner; // define the owner of this contract

// 1️⃣5️⃣ Create Event for creating the tweet, called TweetCreated 
// Use parameters like id, author, content, timestamp
// 1️⃣7️⃣ Create Event for liking the tweet, called TweetLiked (Use parameters like liker, tweetAuthor, tweetId, newLikeCount
    event TweetCreated(uint256 id, address author, string content, uint256 timestamp);
    event TweetLiked(address liker, address tweetAuthor, uint256 tweetId,  uint256newLikedCount);
    event TweetUnliked(address unliker, address tweetAuthor, uint256 tweetId, newLikeCount);

// 8️⃣ create the constructor under all the variables
// Create a constructor function to set an owner of contract
    constructor(){
        owner = msg.sender;
    }

// 9️⃣ Create a modifier called onlyOwner: to check if the owner is calling the function
    modifier onlyowner() { // use modifier to check onlyowner
        require(msg.sender == owner, "You Are Not The Owner");
        _;
    }

// 7️⃣ Add a function called change TweetLength to change max tweet length 
// ( Hint: use newTweetLength as input for function) 
// 🔟 Use onlyOwner on the changeTweetLength function
     function changeTweetLength(uint16 newTweetLength) public onlyOwner {
        MAX_TWEET_LENGTH = newTweetLength;
    }

// 3️⃣ Add function to create a tweet and save it in mapping 
    // store the tweets above in temporary memory
    // key is the address (the msg.sender)
    // msg.sender: whoever is using the blockchain interacting with your code
    // Add the struct to array Test tweets
    function createTweet(string memory _tweet) public {

// 6️⃣ Use require to limit the length of the tweet to be only 280 characters (ep.15)
    // conditional
    // if tweet length <= 280 then we are good, otherwise we revert
    function createTweet(string memory _tweet) public {
    require(bytes(_tweet).length <= MAX_TWEET_LENGTH, "Tweet is too long bro");     

// 1️⃣2️⃣ Set the id to be the Tweet [ ] length (Hint: you do it in the creatTweet function)  
        Tweet memory newTweet = Tweet({
            id: tweets[msg.sender].length,
            author: msg.sender,  
            content: _tweet, 
            timestamp: block.timestamp, 
            likes: 0
        });
        // not only 1 tweet, so use array 
        // push the tweet into the array
        tweets[msg.sender].push(newTweet); 

// 1️⃣6️⃣ Emit the event in the createTweet() function below
        emit TweetCreated(newTweet, id, newTweet.author, newTweet.content, newTweet.timestamp);
     }

// 1️⃣3️⃣ Add a function to like the tweet (Hint: there should be 2 paramenters, id and author 
// 1️⃣5️⃣ Mark both functions external 
        require tweets[author][id].id == id, "TWEET DOES NOT EXISTS";
        function likeTweet(address author, uint256 id) external {
            tweets[author][id].likes++; //likes = likes + 1;

// 1️⃣8️⃣ Emit the event in the likeTweet() function below  
            emit TweetLiked(msg.sender, author, id, tweets[author][id].likes);
        }

// 1️⃣4️⃣ Add a function to unlike the tweet (make sure you can unlike only if likes count is greater than 0) 
// 1️⃣5️⃣ Mark both functions external 
        function unlikeTweet(address author, uint256 id) external {
            require(tweets[author][id].id == id, "TWEET DOES NOT EXISTS");
            require(tweets[author][id].likes > 0, "TWEET HAS NO LIKES");
            tweets[author][id].likes--;

            emit TweetUnLiked(msg.sender, author, id, tweets[author][id].likes);
            // you cannnot decrement the count if the tweet does not exist
            // also the count cannot be negative
        }

// 4️⃣ Create a function to get tweet
    // not only 1 tweet, so use index to specify the tweet
     function getTweet(uint _i) public view returns (Tweet memory) {
        return tweets[msg.sender][_i]; //only check for information
    }

    function getAllTweets(address _owner) public view returns (Tweet[] memory){
        return tweets[_owner];
    }
}

create a twitter contract and a user profile contract (exercise user)

// SPDX-License-Identifier: MIT

// 1️⃣ Save UserProfile to the mapping in the setProfile() function
// HINT: don't forget to set the _displayName and _bio

pragma solidity ^0.8.0;

contract Profile {
    struct UserProfile {
        string displayName;
        string bio;
    }
    string maxSupply = 50;
    mapping(address => UserProfile) public profiles;

    function setProfile(string memory _displayName, string memory _bio) public {
        // CODE HERE 👇
        profiles[msg.sender] = UserProfile(_displayName, _bio);
    }

    function getProfile(address _user) public view returns (UserProfile memory) {
        return profiles[_user];
    }
}

exercise(main)

// SPDX-License-Identifier: MIT

import "@openzeppelin/contracts/access/Ownable.sol";

pragma solidity ^0.8.0;

interface IProfile {
    struct UserProfile {
        string displayName;
        string bio;
    }

// 2️⃣ Add a getProfile() function to the interface ✅ 
    // CODE HERE
    function getProfile (address _user) external view returns (UserProfile memory)
}

contract Twitter is Ownable {

    uint16 public MAX_TWEET_LENGTH = 280;

    struct Tweet {
        uint256 id;
        address author;
        string content;
        uint256 timestamp;
        uint256 likes;
    }
    mapping(address => Tweet[] ) public tweets;
    // profile contract defined here 
    IProfile profileContract;

    // Define the events
    event TweetCreated(uint256 id, address author, string content, uint256 timestamp);
    event TweetLiked(address liker, address tweetAuthor, uint256 tweetId, uint256 newLikeCount);
    event TweetUnliked(address unliker, address tweetAuthor, uint256 tweetId, uint256 newLikeCount);

// 4️⃣ Create a modifier called onlyRegistered that require the msg.sender to have a profile ✅
// HINT: use the getProfile() to get the user
// HINT: check if displayName.length > 0 to make sure the user exists
    modifier onlyRegistered(){
        IProfile.UserProfile memory userProfileTemp = profileContract.getProfile(
        require(bytes(userProfileTemp.displayName).length > 0, "USER NOT REGISTERED");
        _);
    }

// 3️⃣ Initialize the IProfile in the contructor ✅ 
// HINT: don't forget to include the _profileContract address as a input 
    constructor(address _profileContract) {
       profileContract = IProfile(_profileContract);
    }

    function changeTweetLength(uint16 newTweetLength) public onlyOwner {
        MAX_TWEET_LENGTH = newTweetLength;
    }

    function getTotalLikes(address _author) external view returns(uint) {
        uint totalLikes;

        for( uint i = 0; i < tweets[_author].length; i++){
            totalLikes += tweets[_author][i].likes;
        }

        return totalLikes;
    }

    function createTweet(string memory _tweet) public {
        require(bytes(_tweet).length <= MAX_TWEET_LENGTH, "Tweet is too long bro!" );

        Tweet memory newTweet = Tweet({
            id: tweets[msg.sender].length,
            author: msg.sender,
            content: _tweet,
            timestamp: block.timestamp,
            likes: 0
        });

        tweets[msg.sender].push(newTweet);

        // Emit the TweetCreated event
        emit TweetCreated(newTweet.id, newTweet.author, newTweet.content, newTweet.timestamp);
    }

// 5️⃣ ADD the onlyRegistered modified to createTweet, likeTweet, and unlikeTweet function ✅
    function likeTweet(address author, uint256 id) external onlyRegistered {  
        require(tweets[author][id].id == id, "TWEET DOES NOT EXIST");

        tweets[author][id].likes++;

        // Emit the TweetLiked event
        emit TweetLiked(msg.sender, author, id, tweets[author][id].likes);
    }

// 5️⃣ ADD the onlyRegistered modified to createTweet, likeTweet, and unlikeTweet function ✅
    function unlikeTweet(address author, uint256 id) external onlyRegistered {
        require(tweets[author][id].id == id, "TWEET DOES NOT EXIST");
        require(tweets[author][id].likes > 0, "TWEET HAS NO LIKES");
        
        tweets[author][id].likes--;

        emit TweetUnliked(msg.sender, author, id, tweets[author][id].likes );
    }

    function getTweet( uint _i) public view returns (Tweet memory) {
        return tweets[msg.sender][_i];
    }

    function getAllTweets(address _owner) public view returns (Tweet[] memory ){
        return tweets[_owner];
    }

}

Add Account create to Twitter Dapp

useStateVariables

app.js

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