Handling optional boolean values

Question

I'm failing to understand how I can work around the problem I'm experiencing in my own application.

Imagine this example of a struct that models an incoming request and a function that puts the fields from that request into a database.

type NewBooleanRequest struct {
    RequiredString string `json:"requiredString"`
    OptionalBoolean bool `json:"maybeBoolean"`
}

func LogBooleanRequest(req NewBooleanRequest, db *sql.DB) {
    db.Exec("INSERT INTO log (booleanValue, stringValue) VALUES ($1, $2)", req.OptionalBoolean, req.RequiredString)
}

Now this obviously works fine if I know I will be given a value for all fields of my request model, but that's not a common requirement in reality. How do people generally model "optional" semantics for bool values given that bool has a zero value that is valid in essentially all contexts?

Answer 1

This question isn't specific to booleans, it's common for all NULLable types. The simplest solution is to use a pointer (*bool in your example). There are also Nullable values for common types provided by the sql package. sql.NullBool would be the one you want in this case.

Answer 2

Beside the accepted answer, I found this interesting library https://github.com/guregu/null that can deal with nullable value pretty well. It's very useful to declare API request params without messing with sql library on the server routing (which is not so relevant).

For your case, you can write your request like:

type NewBooleanRequest struct {
    RequiredString string `json:"requiredString"`
    OptionalBoolean null.Bool `json:"maybeBoolean"`
}
request := NewBooleanRequest {
    RequiredString: "Your string",
    OptionalBoolean: null.BoolFrom(false)
}

if request.OptionalBoolean.Valid {
    fmt.Println(request.OptionalBoolean.Bool) // Print "false"
} else {
    fmt.Println("request.OptionalBoolean is NULL")
}