JSON / Custom JSON marshaling / Essential Go
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package main
import (
"encoding/json"
"fmt"
"log"
"time"
)
func notCustom() {
type Event struct {
What string
When time.Time
}
e := Event{
What: "earthquake",
When: time.Now(),
}
d, err := json.Marshal(&e)
if err != nil {
log.Fatalf("json.MarshalIndent failed with '%s'\n", err)
}
fmt.Printf("Standard time JSON: %s\n", string(d))
}
type customTime time.Time
const customTimeFormat = `"2006-02-01"`
func (ct customTime) MarshalJSON() ([]byte, error) {
t := time.Time(ct)
s := t.Format(customTimeFormat)
return []byte(s), nil
}
func (ct *customTime) UnmarshalJSON(d []byte) error {
t, err := time.Parse(customTimeFormat, string(d))
if err != nil {
return err
}
*ct = customTime(t)
return nil
}
type Event2 struct {
What string
When customTime
}
func custom() {
e := Event2{
What: "earthquake",
When: customTime(time.Now()),
}
d, err := json.Marshal(&e)
if err != nil {
log.Fatalf("json.Marshal failed with '%s'\n", err)
}
fmt.Printf("\nCustom time JSON: %s\n", string(d))
var decoded Event2
err = json.Unmarshal(d, &decoded)
if err != nil {
log.Fatalf("json.Unmarshal failed with '%s'\n", err)
}
t := time.Time(decoded.When)
fmt.Printf("Decoded custom time: %s\n", t.Format(customTimeFormat))
}
func main() {
notCustom()
custom()
}
Go
INFO