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// deepcopy makes deep copies of things. A standard copy will copy the
// pointers: deep copy copies the values pointed to. Unexported field
// values are not copied.
// Copyright (c)2014-2016, Joel Scoble (, all rights reserved.
// License: MIT, for more details check the included LICENSE file.
package deepcopy
import (
// Interface for delegating copy process to type
type Interface interface {
DeepCopy() interface{}
// Iface is an alias to Copy; this exists for backwards compatibility reasons.
func Iface(iface interface{}) interface{} {
return Copy(iface)
// Copy creates a deep copy of whatever is passed to it and returns the copy
// in an interface{}. The returned value will need to be asserted to the
// correct type.
func Copy(src interface{}) interface{} {
if src == nil {
return nil
// Make the interface a reflect.Value
original := reflect.ValueOf(src)
// Make a copy of the same type as the original.
cpy := reflect.New(original.Type()).Elem()
// Recursively copy the original.
copyRecursive(original, cpy)
// Return the copy as an interface.
return cpy.Interface()
// copyRecursive does the actual copying of the interface. It currently has
// limited support for what it can handle. Add as needed.
func copyRecursive(original, cpy reflect.Value) {
// check for implement deepcopy.Interface
if original.CanInterface() {
if copier, ok := original.Interface().(Interface); ok {
// handle according to original's Kind
switch original.Kind() {
case reflect.Ptr:
// Get the actual value being pointed to.
originalValue := original.Elem()
// if it isn't valid, return.
if !originalValue.IsValid() {
copyRecursive(originalValue, cpy.Elem())
case reflect.Interface:
// If this is a nil, don't do anything
if original.IsNil() {
// Get the value for the interface, not the pointer.
originalValue := original.Elem()
// Get the value by calling Elem().
copyValue := reflect.New(originalValue.Type()).Elem()
copyRecursive(originalValue, copyValue)
case reflect.Struct:
t, ok := original.Interface().(time.Time)
if ok {
// Go through each field of the struct and copy it.
for i := 0; i < original.NumField(); i++ {
// The Type's StructField for a given field is checked to see if StructField.PkgPath
// is set to determine if the field is exported or not because CanSet() returns false
// for settable fields. I'm not sure why. -mohae
if original.Type().Field(i).PkgPath != "" {
copyRecursive(original.Field(i), cpy.Field(i))
case reflect.Slice:
if original.IsNil() {
// Make a new slice and copy each element.
cpy.Set(reflect.MakeSlice(original.Type(), original.Len(), original.Cap()))
for i := 0; i < original.Len(); i++ {
copyRecursive(original.Index(i), cpy.Index(i))
case reflect.Map:
if original.IsNil() {
for _, key := range original.MapKeys() {
originalValue := original.MapIndex(key)
copyValue := reflect.New(originalValue.Type()).Elem()
copyRecursive(originalValue, copyValue)
copyKey := Copy(key.Interface())
cpy.SetMapIndex(reflect.ValueOf(copyKey), copyValue)