Hello World Solidity Sample - EthWaterloo

helloWorld.sol

pragma solidity ^0.4.12;

contract helloworld {

	address private Owner;
    string public sayHello;

	function helloworld() {
		Owner = msg.sender;
		sayHello = "Hello";
	}

	modifier isOwner() { if (msg.sender != Owner) revert(); _ ;}

	event echoInputEvent(address indexed from, bytes32 str);


    //Rejector function (fallback). rejects all payments . also with payable()
    function() public { revert(); }

    function echoFree(bytes32 inputStr) constant public returns(bytes32){
        //constant functions are free, no gas required
        // but they can't change any state or trigger events
        return (inputStr);
    }

    function echo(bytes32 inputStr) public returns(bytes32){
        //Events require gas
        //bytes to str : http://string-functions.com/hex-string.aspx
        echoInputEvent(msg.sender, inputStr);
        return (inputStr);
    }
    
    function hiBack() public isOwner() {
        //isOwner modifier makes sure only owner can call this function
        sayHello = "Hello to you too";
    }
    
}