底层设计：轮询系统-js教程-PHP中文网

Low-Level Design: Polling System

问题陈述

您需要设计并实现一个在线投票系统。系统应允许用户创建、管理和参与民意调查。每个民意调查都包含一个问题和多个答案选项。用户可以对民意调查进行投票并查看结果。

假设：

我们正在使用基于类的实现
我们没有使用额外的数据库来存储此信息
由于不涉及数据库和服务器，因此没有REST API
投票系统的简单低级方法

要求

创建投票：

用户应该能够创建一个包含问题和多个答案选项的新民意调查。
每个民意调查都必须有唯一的标识符、问题、选项列表和创建时间戳。

管理民意调查：

用户应该能够更新现有民意调查的问题或选项。
用户应该能够删除投票。

投票：

用户应该能够对民意调查中的其中一个选项进行投票。
每个用户每次投票只能投票一次。

查看投票结果：

用户应该能够查看当前的投票结果，包括每个选项的得票数。

民意调查数据：

以允许高效检索和更新的方式存储民意调查、选项和投票。
确保数据完整性和一致性，尤其是当多个用户同时投票时。

实施细节

功能/方法：

创建投票

createPoll :

输入：问题（字符串），选项（字符串数组）
输出：pollId（字符串），消息（字符串）
示例：createPoll("你最喜欢的颜色是什么？", ["Red", "Blue", "Green", "Yellow"]) 返回 {"pollId": "123", "message" ：“投票创建成功。”}

更新投票

更新投票 :

输入：pollId（字符串），问题（字符串），选项（字符串数组）
输出：消息（字符串）
示例：updatePoll("123", "更新问题？", ["Option1", "Option2"]) 返回 {"message": "投票更新成功。"}

删除投票

删除投票 :

输入：pollId（字符串）
输出：消息（字符串）
示例：deletePoll("123") 返回 {"message": "投票已成功删除。"}

投票

投票投票 :

输入：pollId（字符串）、userId（字符串）、选项（字符串）
输出：消息（字符串）
示例： voteInPoll("123", "user1", "Option1") 返回 {"message": "投票成功。"}

查看投票结果

viewPollResults :

输入：pollId（字符串）
输出：pollId（字符串），问题（字符串），结果（带有选项键和投票计数值的对象）
示例: viewPollResults("123") returns {"pollId": "123", "question": "你最喜欢的颜色是什么？", "results": {"Red": 10, "Blue “：5，“绿色”：3，“黄色”：2}}

数据模型

民意调查：

{
  "pollId": "123",
  "question": "What is your favorite color?",
  "options": ["Red", "Blue", "Green", "Yellow"],
  "createdAt": "2024-07-11T00:00:00Z"
}

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投票：

{
  "pollId": "123",
  "userId": "user1",
  "option": "Red",
  "timestamp": "2024-07-11T01:00:00Z"
}

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实施细节

这段代码使用 JavaScript 类定义了一个基本的轮询系统。它允许创建、管理和投票。让我们分解一下代码的各个部分：

1. Class Definitions

Poll Class

Purpose: Represents an individual poll.
Constructor Parameters:
- id: A unique identifier for the poll.
- question: The question being asked in the poll.
- options: An array of possible options that users can vote on.
Properties:
- pollId: Stores the unique ID of the poll.
- question: Stores the poll question.
- options: Stores the array of options.
- createdAt: Stores the creation date and time of the poll.

Vote Class

Purpose: Represents an individual vote cast by a user.
Constructor Parameters:
- pollId: The ID of the poll the vote is associated with.
- userId: The ID of the user who cast the vote.
- option: The option that the user voted for.
Properties:
- pollId: Stores the poll ID for which the vote was cast.
- userId: Stores the user ID of the voter.
- option: Stores the option that the user voted for.
- timestamp: Stores the date and time when the vote was cast.

2. PollManager Class

Purpose: Manages the entire polling system, including creating polls, managing votes, and viewing results.

Constructor:

Properties:
- polls: A Map that stores all polls, where the key is the poll ID and the value is the Poll object.
- pollResults: A Map that stores the results of each poll, where the key is the poll ID and the value is another Map that tracks votes for each option.
- userVotes: A Map that stores the votes by each user, where the key is the poll ID and the value is another Map that tracks whether a user has voted in that poll.

Methods:

createPoll(question, options)
- Generates a new poll with a unique ID.
- Initializes the poll results, setting the vote count for each option to 0.
- Stores the poll and returns the generated poll ID.
updatePoll(pollId, question, options)
- Updates the question and options for an existing poll.
- Resets the poll results to 0 for the updated options.
- Returns a success message if the poll is found, otherwise returns "Poll not found."
deletePoll(pollId)
- Deletes a poll by its ID.
- Also removes associated poll results and user votes.
- Returns a success message if the poll is found, otherwise returns "Poll not found."
voteInPoll(pollId, userId, option)
- Allows a user to cast a vote in a specific poll.
- Ensures a user can only vote once per poll.
- Updates the vote count for the selected option if valid.
- Returns appropriate messages depending on whether the vote was successful, the user had already voted, or the poll or option was invalid.
viewPollResults(pollId)
- Returns the results of a specific poll in an array format, where each entry is a tuple of the option and its vote count.
- Returns "Poll not found" if the poll doesn't exist.

3. Example Usage

Poll Creation: A poll is created asking, "What is your favorite color?" with options ["Red", "Blue", "Green", "Yellow"]. The poll ID is generated as "1".
Voting: Multiple users vote in the poll, and the system ensures users can only vote once.
Viewing Results: The poll results are displayed, showing the vote counts for each option.
Updating the Poll: The poll's question and options are updated, resetting the results.
Voting in Updated Poll: A user votes in the updated poll, and the results are displayed.
Poll Deletion: The poll is deleted, and an attempt to view the results afterward confirms the poll no longer exists.

This implementation provides a basic but functional polling system, handling common scenarios such as poll creation, updating, voting, and deletion.

CODE

class Poll {
    constructor(id, question, options) {
        this.pollId = id;
        this.question = question;
        this.options = options;
        this.createdAt = new Date();
    }
}

class Vote {
    constructor(pollId, userId, option) {
        this.pollId = pollId;
        this.userId = userId;
        this.option = option;
        this.timestamp = new Date();
    }
}

class PollManager {
    constructor() {
        this.polls = new Map();
        this.pollResults = new Map();
        this.userVotes = new Map();
    }

    createPoll(question, options) {
        const pollId = (this.polls.size + 1).toString();
        const poll = new Poll(pollId, question, options);
        this.polls.set(pollId, poll);

        const result = new Map();
        options.forEach(option => result.set(option, 0));
        this.pollResults.set(pollId, result);

        return pollId;
    }

    updatePoll(pollId, question, options) {
        const poll = this.polls.get(pollId);
        if (poll) {
            poll.question = question;
            poll.options = options;

            // Update results for the new options
            const result = new Map();
            options.forEach(option => result.set(option, 0));
            this.pollResults.set(pollId, result);

            return "Poll updated successfully.";
        }
        return "Poll not found.";
    }

    deletePoll(pollId) {
        if (this.polls.delete(pollId)) {
            this.pollResults.delete(pollId);
            this.userVotes.delete(pollId);
            return "Poll deleted successfully.";
        }
        return "Poll not found.";
    }

    voteInPoll(pollId, userId, option) {
        const poll = this.polls.get(pollId);
        if (poll) {
            if (!this.userVotes.has(pollId)) {
                this.userVotes.set(pollId, new Map());
            }

            const userVote = this.userVotes.get(pollId);
            if (userVote.get(userId)) {
                return "User has already voted.";
            }

            const result = this.pollResults.get(pollId);
            if (result.has(option)) {
                result.set(option, result.get(option) + 1);
                userVote.set(userId, true);
                return "Vote cast successfully.";
            } else {
                return "Invalid option.";
            }
        }
        return "Poll not found.";
    }

    viewPollResults(pollId) {
        const results = this.pollResults.get(pollId);
        if (results) {
            return Array.from(results.entries());
        }
        return "Poll not found.";
    }
}

// Example usage
const pollManager = new PollManager();

// Creating a poll
const pollId = pollManager.createPoll("What is your favorite color?", ["Red", "Blue", "Green", "Yellow"]);
console.log("Poll created with ID:", pollId);

// Voting in the poll
let voteMessage = pollManager.voteInPoll(pollId, "user1", "Red");
console.log(voteMessage);

voteMessage = pollManager.voteInPoll(pollId, "user2", "Blue");
console.log(voteMessage);

voteMessage = pollManager.voteInPoll(pollId, "user1", "Green");
console.log(voteMessage); // Should inform the user has already voted

// Viewing poll results
let results = pollManager.viewPollResults(pollId);
console.log("Poll results for poll ID", pollId, ":", results);

// Updating the poll
let updateMessage = pollManager.updatePoll(pollId, "What is your favorite primary color?", ["Red", "Blue", "Yellow"]);
console.log(updateMessage);

// Voting in the updated poll
voteMessage = pollManager.voteInPoll(pollId, "user3", "Yellow");
console.log(voteMessage);

// Viewing updated poll results
results = pollManager.viewPollResults(pollId);
console.log("Updated poll results for poll ID", pollId, ":", results);

// Deleting the poll
let deleteMessage = pollManager.deletePoll(pollId);
console.log(deleteMessage);

// Attempting to view results of a deleted poll
results = pollManager.viewPollResults(pollId);
if (typeof results === "string") {
    console.log(results);
}


// Response
// Poll created with ID: 1
// Vote cast successfully.
// Vote cast successfully.
// User has already voted.
// Poll results for poll ID 1 : [['Red', 1], ['Blue', 1], ['Green', 0], ['Yellow', 0]]
// Poll updated successfully.
// Vote cast successfully.
// Updated poll results for poll ID 1 : [['Red', 0], ['Blue', 0], ['Yellow', 1]]
// Poll deleted successfully.
// Poll not found.

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