Solidity智能合约是没法返回json对象、字典、结构体的。
https://vomtom.at/how-to-return-a-mapping-in-solidity-and-web3/
解决方案：返回多个数组，然后在应用层再进行拼接。
// 一定要在文件开头引入这个
pragma experimental ABIEncoderV2;
// 查询某个学生的所有成绩
function select_scores_info(address studentId) public view returns(string[], int[]){
TableFactory tf = TableFactory(0x1001);
Table table = tf.openTable("stu_score");
string memory stuIdStr = addressToString(studentId);
Condition condition = table.newCondition();
condition.EQ("student_id", stuIdStr);
Entries entries = table.select(stuIdStr, condition);
// 初始化数组大小
string[] memory user_courses_list = new string[](uint256(entries.size()));
int[] memory user_scores_list = new int[](uint256(entries.size()));
// 给数组赋值
for(int i=0; i<entries.size(); ++i) {
Entry entry = entries.get(i);
// 添加数组元素
user_courses_list[uint256(i)] = entry.getString("course_name");
user_scores_list[uint256(i)] = entry.getInt("score");
}
return (user_courses_list, user_scores_list);
}
