How to check if a bytes32 represents an empty string?

Question

Why does the require not throw here when I am passing an empty string for the _name param?

function MyContract(bytes32 _name) public {
        require(_name.length > 0);
        name = _name;
    }

Answer 1

The bytes32 type is always exactly 32 bytes. Therefore, its length is always 32. It is unaware of whether it contains a string, number or something else.

I would recommend doing:

require(_name[0] != 0);

to verify that it does not represent an empty string.

Answer 2

I'm doing it like this:

require(_name != bytes32(0));

Answer 3

The solutions above are completely wrong! You can compare bytes32 and an empty string!

require(_name != "");