Assigning null to JSON fields instead of empty strings

Question

Since empty string is the zero/default value for Go string, I decided to define all such fields as interface{} instead. for example

Answer 1

You could use something like sql.NullString,use 'Valid' to check if it is a nil value.

NullString represents a string that may be null. NullString implements the Scanner interface so it can be used as a scan destination:

type NullString struct {
    String string
    Valid  bool // Valid is true if String is not NULL
}

var s NullString
err := db.QueryRow("SELECT name FROM foo WHERE id=?", id).Scan(&s)
...
if s.Valid {
   // use s.String
} else {
   // NULL value
}

Please DO NOT use pointers like below:

type student struct {
  FirstName  *string `json:"first_name"`
  MiddleName *string `json:"middle_name"`
  LastName   *string `json:"last_name"`
}

Because you need check nil value and dereference like below everywhere,and maybe cause unexpected crash somewhere:

if obj.FirstName != nil {
   fmt.Print("%s", *obj.FirstName)
}

I have compared two solution and choosed former method in my extensively production code,it work ok.