I would like to create a base struct which have to method, I want to use these methods in the substructs. For example:
type Base struct {
Type string `json:"$type"`
}
func (b Base) GetJSON() ([]byte, error) {
return json.Marshal(b)
}
func (b Base) SetType(typeStr string) interface{} {
b.Type = typeStr
return b
}
In the new struct I want to use it like this:
type Auth struct {
Base
Username
Password
}
and call these methods in the main:
func main() {
a := Auth{
Username: "Test",
Password: "test",
}
a = a.SetType("testtype").(Auth)
j, _ := a.GetJSON()
}
In the SetType case I got a panic caused by interface{} is not Auth type, it is Base type. In the GetJSON case I got a json about the Type, but only the Type.
Is there any solution for the problem what I want to solve?
As mentioned in the comments, embedding is not inheritance but composition, so you'll probably have to either:
In the particular case you are showing (trying to get GetJSON() to include also the fields of the outer struct, here is a possible way of getting that to work that does not require many changes (just storing a pointer to the outer struct in Base when creating the struct):
package main
import (
"encoding/json"
"fmt"
)
type Base struct {
Type string `json:"$type"`
selfP interface{} // this will store a pointer to the actual sub struct
}
func (b *Base) SetSelfP(p interface{}) {
b.selfP = p
}
func (b *Base) GetJSON() ([]byte, error) {
return json.Marshal(b.selfP)
}
func (b *Base) SetType(typeStr string) {
b.Type = typeStr
}
type Auth struct {
Base
Username string
Password string
}
func main() {
a := &Auth{
Username: "Test",
Password: "test",
}
a.SetSelfP(a) // this line does the trick
a.SetType("testtype")
j, _ := a.GetJSON()
fmt.Println(string(j))
}
Playground link: https://play.golang.org/p/npuy6XMk_t