Making a Birthday Contract.

Intermediate Solidity Ethereum Notes & Development.

Let’s make a Birthday smart contract in Solidity.

Note/selfplug: If you are looking for an introduction to Ethereum, Solidity and Smart Contracts I just published an eBook on getting started:
https://www.amazon.com/dp/B078CQ8L7V

The Problem / challenge:

• To have a contract record it’s birth on the blockchain.
• To have the contract tell you it’s Birthday.
• Bonus / Extra Credit: Return the Birthday in a Human Readable way without the need of external UI’s.

The contract :

pragma solidity ^ 0.4.0;
contract DateTime {
        function getYear(uint timestamp) public constant returns (uint16);
        function getMonth(uint timestamp) public constant returns (uint8);
        function getDay(uint timestamp) public constant returns (uint8);
}
contract BirthDay {
  uint public bday;
  address public dateTimeAddr = 0x8Fc065565E3e44aef229F1D06aac009D6A524e82;
  DateTime dateTime = DateTime(dateTimeAddr);
  function BirthDay() public  {
    bday = now;
  }
  function getBirthYear() view public returns (uint16){
      return dateTime.getYear(bday);
  }
  function getBirthMonth() view public returns (uint8){
      return dateTime.getMonth(bday);
  }
  function getBirthDay() view public returns (uint8){
      return dateTime.getDay(bday);
  }
}

Read the Contract :

https://kovan.etherscan.io/address/0x86d686cc0e2feaa63834163af8b7a5fb869bb977#readContract

Development Notes :

The first thing this contract does is record it’s birthday via the now native function which is saved into a variable bday by the constructor:

uint public bday;
function BirthDay() public  {…