when msg.sender is the owner?

Question

how do I know if the msg.sender is the owner (the person that deployed) of the contract or a random address that interacted with the contract? in this case for example:

    address payable owner  =  msg.sender;   

    modifier onlyOwner(){
        require(msg.sender == owner);
        _;
    }
    function close() public onlyOwner { 
    selfdestruct(owner);  
}
    

why isn't the msg.sender reset at each interaction?

Answer 1

Solidity enables constructors which have code executed at contract creation. So you need to instantiate owner in the constructor to catch the contract deployer address :

address payable owner;
constructor() public {
owner = msg.sender;
}

There are also standardized contracts to manage ownership. Exemple of implementation can be found here : https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol.