Represent optionality

Use nil (i.e. ()) to represent optional values.

Note: Use () instead of null unless it’s in a json context.

Example 1:

Use nil to indicate the unavailability of value.

Bad Code

type Employee record {
   string middleName = ""; //middleName is not specified
};

Good Code

type Employee record {
   string? middleName = ();
};

Example 2:

Return nil to indicate the unavailability of value.

Bad Code

function getMarks(string name) returns int {
    if marks.hasKey(name) {
        return marks.get(name);
    }
    return -1;
}

Good Code

function getMarks(string name) returns int? {
    if marks.hasKey(name) {
        return marks.get(name);
    }
    return ();
}

See Also:

• nil