Repository with items and save method replacing existing values

repo_save_method.go

package main

import (
	"fmt"
	"encoding/json"
)

type ID struct {
	ID string
}

type Data struct {
	ID      ID
	Payload string
}

type Repository struct {
	Items []*Data
}

func NewRepository() *Repository {
	return &Repository {
		Items: make([]*Data, 0),
	}
}

func (r *Repository) Save(data *Data) error {
	for i, item := range r.Items {
		if item.ID == data.ID {
			// Clone the object
			// *item = *data
			
			// Pass a reference
			r.Items[i] = data

			return nil
		}
	}
	
	r.Items = append(r.Items, data)
	
	return nil
}

func main() {
	repo := NewRepository()
	repo.Items = []*Data{
		&Data{ID{"entity1"}, "data1"},
		&Data{ID{"entity2"}, "data2"},
		&Data{ID{"entity3"}, "data3"},
		&Data{ID{"entity4"}, "data4"},
	}
	
	// newItem := &Data{ID{"entity5"}, "data5"}
	newItem := &Data{ID{"entity2"}, "data5"}
	repo.Save(newItem)
	newItem.Payload = "new_data"

	s, _ := json.MarshalIndent(repo.Items, "", "  ")
	fmt.Printf("%s", s)
}