65 lines
1.3 KiB
Go
65 lines
1.3 KiB
Go
// For more tutorials: https://blog.learngoprogramming.com
|
|
//
|
|
// Copyright © 2018 Inanc Gumus
|
|
// Learn Go Programming Course
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
|
//
|
|
|
|
package main
|
|
|
|
import (
|
|
"encoding/json"
|
|
"fmt"
|
|
"strconv"
|
|
"time"
|
|
)
|
|
|
|
type book struct {
|
|
product
|
|
Published interface{}
|
|
}
|
|
|
|
func (b book) String() string {
|
|
p := format(b.Published)
|
|
return fmt.Sprintf("%s - (%v)", &b.product, p)
|
|
}
|
|
|
|
// MarshalJSON is an implementation of the json.Marshaler interface.
|
|
// json.Marshal and Decode call this method.
|
|
func (b *book) MarshalJSON() ([]byte, error) {
|
|
// Calling Marshal creates an infinite loop because Marshal calls
|
|
// MarshalJSON again and again.
|
|
//
|
|
// Declaring a clone type without MarshalJSON fixes the problem.
|
|
type jbook book
|
|
|
|
// book is convertable to jbook
|
|
// jbook's underlying type is book.
|
|
jb := (*jbook)(b)
|
|
|
|
// Customize the formatting of the published field.
|
|
// This will result in the published field of the resulting json.
|
|
jb.Published = format(b.Published)
|
|
|
|
return json.Marshal(jb)
|
|
}
|
|
|
|
func format(v interface{}) string {
|
|
var t int
|
|
|
|
switch v := v.(type) {
|
|
case int:
|
|
t = v
|
|
case string:
|
|
t, _ = strconv.Atoi(v)
|
|
default:
|
|
return "unknown"
|
|
}
|
|
|
|
// Mon Jan 2 15:04:05 -0700 MST 2006
|
|
const layout = "2006/01"
|
|
|
|
u := time.Unix(int64(t), 0)
|
|
return u.Format(layout)
|
|
}
|