# Smart Contract 작성

이 가이드에서 작성할 Dapp은 간단한 election application 입니다. 스마트 컨트랙트 자체에 대한 설명은 아래 블로그글을 참고하세요.

{% embed url="<http://www.dappuniversity.com/articles/the-ultimate-ethereum-dapp-tutorial>" %}

1. 이 스마트 컨트랙트는 미리 만들어둔 pet-shop truffle box를 이용합니다. 우선 terminal에 새로운 폴더를 만들고, 아래 명령어를 실행하세요.

```
mkdir election
```

```
cd election
```

```
truffle unbox pet-shop
```

2\. election.sdl 파일을 만듭니다.

```
touch contracts/Election.sol
```

```
pragma solidity ^0.4.2;

contract Election {
    // Model a Candidate
    struct Candidate {
        uint id;
        string name;
        uint voteCount;
    }

    // Store accounts that have voted
    mapping(address => bool) public voters;
    // Read/write candidates
    mapping(uint => Candidate) public candidates;
    // Store Candidates Count
    uint public candidatesCount;

    event votedEvent (
        uint indexed _candidateId
    );

    function Election () public {
        addCandidate("Pantera");
        addCandidate("X X");
    }

    function addCandidate (string _name) private {
        candidatesCount ++;
        candidates[candidatesCount] = Candidate(candidatesCount, _name, 0);
    }

    function vote (uint _candidateId) public {
        // require that they haven't voted before
        // require(!voters[msg.sender]);

        // require a valid candidate
        require(_candidateId > 0 && _candidateId <= candidatesCount);

        // record that voter has voted
        voters[msg.sender] = true;

        // update candidate vote Count
        candidates[_candidateId].voteCount ++;
        
        // trigger voted event
        votedEvent(_candidateId);
    }
}
```

\*\* copy & paste 했을 때, encoding error가 난다면, 위에 있는 링크로 가서 코드를 가져오세요.

3\. truffle을 이용해 ethereum blockchain에 migration하기 위해 migration 파일을 만듭니다.

```
touch migrations/2_deploy_contracts.js
```

```
var Election = artifacts.require("./Election.sol");

module.exports = function(deployer) {
  deployer.deploy(Election);
};
```

4\. 새로운 터미널 창을 띄워서 migration을 진행합니다.

```
truffle migrate
```

* 만약 ethereum client를 찾지 못한다는 error가 발생한다면, ./truffle.js의 port number가 9545인지 확인하세요.
* 수정후 배포를 하는것이라면 **truffle migrate --reset** 을 이용하세요.

![](/files/-LRzGNfDD6DGhwXlkbIB)

6\. console을 이용해서, 컨트랙트를 확인해 볼 수 있습니다.

```
truffle console 
```

```
Election.deployed().then(function(instance) { app = instance })
```

![](/files/-LRzITKlN6DxSAUqGtCq)


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://sgwanlee.gitbook.io/morpheus-labs/simple-dapp/undefined.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.