unmarshal json field is int or string [duplicate] - go

Question

This question already has an answer here:
How to unmarshal a field that can be an array or a string in Go?
(1 answer)
Closed 3 years ago.
I have an app where the type is
type Person struct {
Name string `json:"name"`
Age int `json:"age"`
}
But we have legacy clients that send the Age field as either a string or an integer, so...
{
"name": "Joe",
"age": "42"
}
OR
{
"name": "Joe",
"age": 42
}
I know I can annotate the "age" field with ",string" if it's a string that I want coerced into an integer, but what if the field could be either one?

Answer 1

Check out "json - raw Message" in the docs, from there on out you can try to parse it however you want. Example below and on GoPlayground
package main
import (
"encoding/json"
"fmt"
"log"
"strconv"
"unicode/utf8"
)
type Person struct {
Name string `json:"name"`
Age json.RawMessage `json:"age"`
}
func main() {
var j = []byte(`{"name": "Joe","age": "42"}`)
var j2 = []byte(`{"name": "Joe","age": 42}`)
stringOrInt(j)
stringOrInt(j2)
}
func stringOrInt(bytes []byte) {
var p Person
err := json.Unmarshal(bytes, &p)
if err != nil {
log.Fatal(err)
}
if utf8.Valid(p.Age) {
i, err := strconv.Atoi(string(p.Age))
if err != nil {
fmt.Println("got int " + strconv.Itoa(i))
} else {
fmt.Println("got string")
}
} else {
fmt.Println("whoops")
}
}

Answer 2

package main
import (
"encoding/json"
"fmt"
"strconv"
)
type Person struct {
Name string `json:"name"`
Age int `json:"age"`
}
func (p *Person) UnmarshalJSON(b []byte) error {
var objMap map[string]*json.RawMessage
err := json.Unmarshal(b, &objMap)
if err != nil {
return err
}
var name string
err = json.Unmarshal(*objMap["name"], &name)
if err != nil {
return err
}
var ageInt int
err = json.Unmarshal(*objMap["age"], &ageInt)
if err != nil {
// age is string
var ageString string
err = json.Unmarshal(*objMap["age"], &ageString)
if err != nil {
return err
}
aI, err := strconv.Atoi(ageString)
if err != nil {
return err
}
p.Age = aI
} else {
p.Age = ageInt
}
p.Name = name
fmt.Printf("%+v", *p)
return nil
}
func main() {
p := `{"name": "John", "age": "10"}`
// p := `{"name": "John", "age": 10}`
newP := Person{}
err := newP.UnmarshalJSON([]byte(p))
if err != nil {
fmt.Printf("Error %+v", err)
}
}
https://play.golang.org/p/AK8H_wdNqmt
You can try something like this. Try to read and parse Into int, if that fails check for string value, parse it to int and then assign int value to person struct