1 編寫(xiě)智能合約

每個(gè)學(xué)生分別部署合約Student.sol ，保證只有自己可以修改姓名。老師部署合約StudentScore.sol，用于錄入學(xué)生成績(jī)，查詢(xún)學(xué)生信息。查詢(xún)學(xué)生信息時(shí)，需要調(diào)用學(xué)生部署的合約Student.sol。
student.sol合約，用于學(xué)生對(duì)自己信息進(jìn)行管理。

• 學(xué)生的基本信息作為狀態(tài)變量：

	pragma solidity ^0.4.0;
	contract Student{
	    string studentID;
	    string studentName;
	    address owner;
	}

• 聲明構(gòu)造函數(shù)，在構(gòu)造函數(shù)中將owner設(shè)置為調(diào)用者的address：

	constructor(string _studentID, string _stdentName) public{
		studentID = _studentID;
		studentName = _stdentName;
		owner = msg.sender;
	}

• 聲明函數(shù)修飾器，可以將其加在函數(shù)中，在函數(shù)執(zhí)行前進(jìn)行判斷，來(lái)檢查調(diào)用者是否為學(xué)生本人，只有本人才能調(diào)用該函數(shù)：

	modifier onlyOwner(){
    	require(msg.sender == owner,"only owner can call this function");
    	_;
	}

• get和set方法，其中set方法加入了函數(shù)修飾器：

    function getStudentIDandName() public constant returns(string,string) {
    	return (studentID,studentName);
    }

    function setStudentIDandName(string _studentID,string _studentName) public onlyOwner {
    	studentID = _studentID;
    	studentName = _studentName;
    }

Teacher.sol合約，用于錄入、查詢(xún)學(xué)生成績(jī)文章來(lái)源地址http://www.zghlxwxcb.cn/news/detail-465875.html

• 導(dǎo)入Student合約：

	pragma solidity ^0.4.11;
	import "./Student.sol";

• 學(xué)生的相關(guān)成績(jī)作為狀態(tài)變量，totalScore為全班總成績(jī)，studentCount全班學(xué)生數(shù)量，owner部署合約的賬戶(hù)地址。同時(shí)聲明映射studentAddrMap，studentScoreMap，將學(xué)生ID分別映射為學(xué)生地址和學(xué)生成績(jī)。事件studentNotExistsEvent用于存儲(chǔ)學(xué)生ID號(hào)

	contract StudentScore{
	    uint totalScore;
	    uint studentCount;
	    address owner;
	    mapping(string => address) studentAddrMap;
	    mapping(string => uint) studentScoreMap;
	    event studentNotExistsEvent(string studentID);
	}

• 聲明自定義修飾符onlyOwner，只有老師地址才能執(zhí)行這些函數(shù)。

	modifier onlyOwner(){
        require(msg.sender == owner,"only owner can call this function");
        _;
    }

• 函數(shù)addStudentScore，modifyScoreByStudentId分別用于老師添加或修改學(xué)生成績(jī)：

    function addStudentScore(string studentID, address student, uint score) public onlyOwner {    
        studentAddrMap[studentID] = student;
        studentScoreMap[studentID] = score;
        totalScore += score;
        studentCount ++;
    }
    
    function modifyScoreByStudentId(string studentID, uint score) public onlyOwner{
        if(!studentExists(studentID)) {
            studentNotExistsEvent(studentID);
            return;
        }
        totalScore -= studentScoreMap[studentID];
        studentScoreMap[studentID] = score;
        totalScore += score; 
    }

• 函數(shù)getAvgScore用于查詢(xún)?nèi)鄬W(xué)生平均成績(jī)，函數(shù)studentExists用于判斷學(xué)生ID是否存在，函數(shù)getScoreByStudentID用于學(xué)生查詢(xún)自己的成績(jī)。

    function getAvgScore() public view returns(uint){    
        return totalScore / studentCount;
    }
    function studentExists(string studentID) public view returns(bool){
        address student = Student(studentAddrMap[studentID]);
        if(student == 0x00){
            return false;
        }else{
            return true;
        }
    }
    function getScoreByStudentID(string studentID) public constant returns(string, string, uint){
        if(!studentExists(studentID)) {
            studentNotExistsEvent(studentID);
            return;
        }
        Student student = Student(studentAddrMap[studentID]);
        var studentName = student.getStudentName();
        uint score = studentScoreMap[studentID];
        return(studentID, studentName, score);
    }

到了這里，關(guān)于以太坊智能合約開(kāi)發(fā)（五）：Solidity成績(jī)錄入智能合約實(shí)驗(yàn)的文章就介紹完了。如果您還想了解更多內(nèi)容，請(qǐng)?jiān)谟疑辖撬阉鱐OY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！