How Can I Best Represent Optional Strings in Go?

Idiomatic Go: Representing Optional Strings

The absence of variant types in Go poses a challenge for modeling values that can exist in either an absent or present form. This is particularly relevant for strings, which cannot accept nil as a member.

Options for Modeling Optional Strings

1. string: Although using a pointer to string (string) could work, it introduces awkwardness in operations such as referencing string literals.
2. Wrapper: Encapsulating the string and its presence status in a wrapper is a viable solution, but it deviates from the goal of using just a string.

3. string with Specific Null Value:

   a. Empty String (""): Designating the empty string as the null element provides convenience for initialization and handling absent values from maps.

   b. Invalid UTF-8 Byte Sequence: For cases where empty strings are valid, a short invalid UTF-8 byte sequence (e.g., "xff") can be employed to represent the null value while allowing valid text strings.

Using Invalid UTF-8 Byte Sequence

1. Define a constant, such as const Null = "xff", to represent the null value.
2. This approach allows both empty strings and valid texts as optional values.
3. The utf8.ValidString() function can be used to check if a string is a valid text.

Example:

const Null = "\xff"

func main() {
    fmt.Println(utf8.ValidString(Null)) // false

    s := Null
    fmt.Println([]byte(s)) // [255]
    fmt.Println(s == Null) // true
    s = "notnull"
    fmt.Println(s == Null) // false
}

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