go structures, methods and tags / published by https://github.com/dacr/code-examples-manager #b9b7e1b1-41c0-4ae5-a3d5-7b29d251a040/b1c393b9ea8519c98236dfa28eeeb956e36439c1

structures-methods-tags.go

/*?sr/bin/true; exec /usr/bin/env nix-shell -p go --run "go run $0" #*/
// summary : go structures, methods and tags
// keywords : go, structures, methods, tags, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : b9b7e1b1-41c0-4ae5-a3d5-7b29d251a040
// created-on : 2025-03-27T11:10:41+01:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : nix-shell -p go --run "go run $file"
package main

import (
	"encoding/json"
	"encoding/xml"
	"fmt"
	"time"
)

type GenderType string

const (
	Male   GenderType = "male"
	Female GenderType = "female"
)

// ======================================================================================================

type Person struct {
	FirstName string     `json:"first_name" xml:"firstName"`
	LastName  string     `json:"last_name" xml:"lastName"`
	Age       int        `json:"age" xml:"age"`
	Gender    GenderType `json:"gender" xml:"gender"`
	BirthDate time.Time  `json:"birth_date,omitempty" xml:"birthDate,omitempty" format:"iso8601"`
}

// default toString method !
func (me Person) String() string {
	return fmt.Sprintf("%s %s (%d)", me.FirstName, me.LastName, me.Age)
}

func (me Person) IsMale() bool { // travail sur une copie d'une personne
	return me.Gender == Male
}

func (me *Person) SetAge(age int) { // travail sur une référence, donc la mise à jour est effective
	me.Age = age // du coup ne pas oublier la syntaxe pointeur
}

func (me Person) SetAgeBAD(age int) {
	me.Age = age // mise à jour sur la copie !! Donc pas de mise à jour de la structure originale
}

// ======================================================================================================

func johnDoe1() Person {
	someone := Person{}
	someone.FirstName = "John"
	someone.LastName = "Doe"
	someone.Age = 30
	someone.Gender = Male
	someone.BirthDate = time.Now()
	return someone
}

func johnDoe2() Person {
	someone := Person{
		FirstName: "John",
		LastName:  "Doe",
		Age:       30,
		Gender:    Male,
		BirthDate: time.Now(),
	}
	return someone
}

func main() {
	john := johnDoe2()
	john.SetAge(42)

	fmt.Println(john)

	johnJSON, err := json.MarshalIndent(john, "", "  ")
	if err != nil {
		fmt.Println("Error marshalling john to JSON:", err)
		return
	}
	fmt.Println(string(johnJSON))

	johnXML, err := xml.MarshalIndent(john, "", "  ")
	if err != nil {
		fmt.Println("Error marshalling john to XML:", err)
		return
	}
	fmt.Println(string(johnXML))
}