I will write a smart contract about patient medical records. And I have an example for this. But all data stored in struct. I want to use time-series data. As far as know, I have to use array of struct, but I don’t know how can i do that?

Can you help me please?

contract MedicalHistory {
    enum Gender {
        Male,
        Female
    }
    uint _patientCount = 0;

    struct Patient {
        string name;
        uint16 age;
        //max of uint16 is 4096
        //if we use uint8 the max is uint8
        string telephone;
        string homeAddress;
        uint64 birthday; //unix time
        string disease; //disease can be enum
        uint256 createdAt; // save all history
        Gender gender;
    }

    mapping(uint => Patient) _patients;

    function Register(
        string memory name,
        uint16 age,
        string memory telephone,
        string memory homeAddress,
        uint64 birthday,
        string memory disease,
        // uint256 createdAt,
        Gender gender
    }
}

This is the code snippet from my smart contract.. How can I convert struct to array?

>Solution :

You can .push() into a storage array, effectively adding new item.

I simplified the code example just so it’s easier to see the actual array manipulation:

pragma solidity ^0.8;

contract MedicalHistory {
    struct Patient {
        string name;
        uint16 age;
    }

    Patient[] _patients;

    function Register(
        string memory name,
        uint16 age
    ) external {
        Patient memory patient = Patient(name, age);
        _patients.push(patient);
    }
}

Please note that if you’re using a public network such as Ethereum, all stored data is retrievable even though it’s stored in a non-public property by querying the contract storage slots. See this answer for a code example. So unless this is just an academic exercise, I really don’t recommend storing health and other sensitive data on the blockchain.