Go語言中所有賦值操作都是值傳遞，如果結構中不含指針，則直接賦值就是深度拷貝；如果結構中含有指針（包括自定義指針，以及切片，map等使用了指針的內置類型），則數據源和拷貝之間對應指針會共同指向同一塊內存，這時深度拷貝需要特別處理。目前，有三種方法，一是用gob序列化成字節序列再反序列化生成克隆對象；二是先轉換成json字節序列，再解析字節序列生成克隆對象；三是針對具體情況，定製化拷貝。前兩種方法雖然比較通用但是因爲使用了reflex反射，性能比定製化拷貝要低出2個數量級，所以在性能要求較高的情況下應該儘量避免使用前兩者。
結論數據：
執行一次的時間
gob time:454µs
json time:170µs
custom time:2µs
測試代碼如下：
package main
import (
"bytes"
"encoding/gob"
"encoding/json"
"fmt"
"time"
)
type AuthorInfo struct {
Name string `json:name`
Age int `json:age`
Country *int `json:country`
}
type Book struct {
Title string `json:title`
Author AuthorInfo `json:author`
Year int `json:year`
Category []string `json:category`
Price map[string]string `json:price`
}
func DeepCopyByGob(dst, src interface{}) error {
var buffer bytes.Buffer
if err := gob.NewEncoder(&buffer).Encode(src); err != nil {
return err
}
return gob.NewDecoder(&buffer).Decode(dst)
}
func DeepCopyByJson(src []Book) (*[]Book, error) {
var dst = new([]Book)
b, err := json.Marshal(src)
if err != nil {
return nil, err
}
err = json.Unmarshal(b, dst)
return dst, err
}
func DeepCopyByCustom(src []Book) []Book {
dst := make([]Book, len(src))
for i, book := range src {
tmpbook := Book{}
tmpbook.Title = book.Title
tmpbook.Year = book.Year
tmpbook.Author = AuthorInfo{}
tmpbook.Author.Name = book.Author.Name
tmpbook.Author.Age = book.Author.Age
tmpbook.Author.Country = new(int)
*tmpbook.Author.Country = *book.Author.Country
tmpbook.Category = make([]string, len(book.Category))
for index, category := range book.Category {
tmpbook.Category[index] = category
}
tmpbook.Price = make(map[string]string)
for k, v := range book.Price {
tmpbook.Price[k] = v
}
dst[i] = tmpbook
}
return dst
}
func check(err error){
if err != nil{
panic(err)
}
}
func print(name string, books []Book){
for index,book := range books{
fmt.Printf("%s[%d]=%v country=%d\n", name, index, book, *book.Author.Country)
}
}
func main() {
//初始化源Book切片
books := make([]Book, 1)
country := 1156
author := AuthorInfo{"David", 38, &country}
price := make(map[string]string)
price["Europe"] = "$56"
books[0] = Book{"Tutorial", author, 2020, []string{"math", "art"}, price}
print("books",books)
var err error
var start time.Time
//Gob拷貝
start = time.Now()
booksCpy := make([]Book, 1)
err = DeepCopyByGob(&booksCpy, books)
fmt.Printf("\ngob time:%v\n", time.Now().Sub(start))
check(err)
*booksCpy[0].Author.Country = 1134
booksCpy[0].Category[0] = "literature"
booksCpy[0].Price["America"] = "$250"
print("booksCpy",booksCpy)
print("books",books)
//JSON拷貝
start = time.Now()
booksCpy2, err_json := DeepCopyByJson(books)
fmt.Printf("\njson time:%v\n", time.Now().Sub(start))
check(err_json)
*(*booksCpy2)[0].Author.Country = 1135
(*booksCpy2)[0].Category[0] = "science"
(*booksCpy2)[0].Price["Canada"] = "$150"
print("(*booksCpy2)",*booksCpy2)
print("books",books)
//定製拷貝
start = time.Now()
booksCpy3 := DeepCopyByCustom(books)
fmt.Printf("\ncustom time:%v\n", time.Now().Sub(start))
*booksCpy3[0].Author.Country = 1136
booksCpy3[0].Category[0] = "geometry"
booksCpy3[0].Price["Africa"] = "$34"
print("booksCpy3",booksCpy3)
print("books",books)
}
運行輸出：
books[0]={Tutorial {David 38 0xc000016178} 2020 [math art] map[Europe:$56]} country=1156
gob time:454.117µs
booksCpy[0]={Tutorial {David 38 0xc0000165d8} 2020 [literature art] map[America:$250 Europe:$56]} country=1134
books[0]={Tutorial {David 38 0xc000016178} 2020 [math art] map[Europe:$56]} country=1156
json time:170.338µs
(*booksCpy2)[0]={Tutorial {David 38 0xc000016878} 2020 [science art] map[Canada:$150 Europe:$56]} country=1135
books[0]={Tutorial {David 38 0xc000016178} 2020 [math art] map[Europe:$56]} country=1156
custom time:2.165µs
booksCpy3[0]={Tutorial {David 38 0xc0000168c8} 2020 [geometry art] map[Africa:$34 Europe:$56]} country=1136
books[0]={Tutorial {David 38 0xc000016178} 2020 [math art] map[Europe:$56]} country=1156
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