How can contract ownership be transferred from one account to another?

Question

I have a contract belonging to one of my accounts. How can I transfer ownership to another account?

Answer 1

Your contract needs to implement an ownership transfer function. This will do it:

address public owner;
function transfer(address newOwner) public {
    if (msg.sender != owner) throw;
    owner = newOwner;
}

People often put this in an Owned contract, which you can inherit from in other contracts. For example:

contract Owned {
    address public owner;
    modifier onlyOwner() {
        if (msg.sender != owner) throw;
        _;
    }
    function transfer(address newOwner) public onlyOwner {
        owner = newOwner;
    }
}

Then in your other contracts:

contract myContract is Owned {
    function test() public onlyOwner {
        //....
    }
}

Answer 2

There is a catch in previous answer. The ownership would be transferred even if the owner sends a blank address by mistake. A better way would be to add a check before transferring ownership.

modifier onlyOwner() {
    if (msg.sender != owner) throw;
    _;
}
function transferOwnership (address newOwner) onlyOwner{
    //check if not empty
    if (newOwner != 0x0){
        owner = newOwner;
    }
}