Checking for Empty Integer in Golang

Question

I am designing an API where a user sends integer values and some operation is performed depending on the value sent. During the validation check that whether this value exists in the request, I have to equate it to 0 i.e. if intValue == 0.

However, I also have to perform a different operation in case the value is 0. Is there any way I can check that the integer does not exist or is empty without equating to 0?

Note: The requirements are set by the client and I cannot change them.

Answer 1

When decoding JSON data into a struct, you can differentiate optional fields by declaring them as a pointer type.

For example:

type requestFormat struct {
    AlwaysPresent int
    OptionalValue *int
}

Now when the value is decoded, you can check if the value was supplied at all:

var data requestFormat

err := json.NewDecoder(request.Body).Decode(&data)
if err != nil { ... }

if data.OptionalValue == nil {
    // OptionalValue was not defined in the JSON data
} else {
    // OptionalValue was defined, but it still may have been 0
    val := *data.OptionalValue
}