Lecture 6 Blockchain Homework

ContactBook.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >0.8.2;

 // unsigned integer
contract ContactBook {

    // dynamic data types
    string public myName;
    string[] names;


    // static data types
    uint256 public myAge;
    uint256[] ages;

    address public myAddress;
    address[] addresses;


    mapping(address => string) public addressesToNames;

    constructor(address _address,uint256 _age, string memory _name) public {
        myAddress = _address;
        setAge(_age);
        setName(_name);
    }

    function addContact(address _address, uint256 _age, string memory _name) public onlyOwner {
        names.push(_name);
        ages.push(_age);
        addresses.push(_address);
        addressesToNames[_address]=_name;
    }

    function getNameByIndex(uint256 _index) view public returns(string memory){
        return names[_index];
    }

    function getAgeByIndex(uint256 _index) view public returns(uint256){
        return ages[_index];
    }

    function getAddressByIndex(uint256 _index) view public returns(address){
        return addresses[_index];
    }



    /**
     * @dev Store value in variable
     * @param _num value to set
     */
    function setAge(uint256 _num) public onlyOwner{
        myAge = _num;
    }

    function setName(string memory _name) public onlyOwner{
        myName = _name;
    }

    function setAddress(address _address) public onlyOwner {
        myAddress = _address;
    }
    
    function hello() external view returns (string memory){
        return string.concat("Hello ",myName);
    }

    modifier onlyOwner(){
        require(msg.sender == myAddress);
        _;
    }
}