Why does my Go code not run?

package main

import (
	"fmt"
	"github.com/ant0ine/go-json-rest"
	"net/http"
)

type App struct {
	Id   string
	Name string
}

func GetApp(w *rest.ResponseWriter, req *rest.Request) {
	user := App{
		Id:   req.PathParam("id"),
		Name: "Antoine",
	}
	w.WriteJson(&user)
}

type MyResourceHandler struct {
	rest.ResourceHandler
}

type ResourceController interface {
	Show(w *rest.ResponseWriter, req *rest.Request)
	Create(w *rest.ResponseWriter, req *rest.Request)
	Update(w *rest.ResponseWriter, req *rest.Request)
	Delete(w *rest.ResponseWriter, req *rest.Request)
}

func (self *MyResourceHandler) AddResource(name string, c ResourceController) error {
	show_func := func(w *rest.ResponseWriter, r *rest.Request) {
		c.Show(w, r)
	}
	create_func := func(w *rest.ResponseWriter, r *rest.Request) {
		c.Create(w, r)
	}
	update_func := func(w *rest.ResponseWriter, r *rest.Request) {
		c.Update(w, r)
	}
	delete_func := func(w *rest.ResponseWriter, r *rest.Request) {
		c.Delete(w, r)
	}

	err := self.ResourceHandler.SetRoutes(
		rest.Route{"GET", fmt.Sprintf("/%s/:id", name), show_func},
		rest.Route{"POST", fmt.Sprintf("/%s", name), create_func},
		rest.Route{"PUT", fmt.Sprintf("/%s/:id", name), update_func},
		rest.Route{"DELETE", fmt.Sprintf("/%s/:id", name), delete_func},
	)
	return err
}

type AppController struct{}

func (self *AppController) Show(w *rest.ResponseWriter, r *rest.Request) {
	app := App{
		Id:   r.PathParam("id"),
		Name: "Antoine",
	}
	w.WriteJson(&app)
}

func (self *AppController) Create(w *rest.ResponseWriter, r *rest.Request) {
	app := App{
		Id:   r.PathParam("id"),
		Name: "Antoine",
	}
	w.WriteJson(&app)
}

func (self *AppController) Update(w *rest.ResponseWriter, r *rest.Request) {
	app := App{
		Id:   r.PathParam("id"),
		Name: "Antoine",
	}
	w.WriteJson(&app)
}

func (self *AppController) Delete(w *rest.ResponseWriter, r *rest.Request) {
	app := App{
		Id:   r.PathParam("id"),
		Name: "Antoine",
	}
	w.WriteJson(&app)
}

func main() {
	handler := MyResourceHandler{}
	controler := AppController{}
	handler.AddResource("app", controler)
	http.ListenAndServe(":9008", &handler)
}

I have implemented all of four methods of interface ResourceController, but it tells me:

./fakeapi.go:93: cannot use controler (type AppController) as type ResourceController in function argument:
	AppController does not implement ResourceController (Create method requires pointer receiver)

It's in the error message: (Create method requires pointer receiver)

You've defined Create on *AppController (pointer to an AppController), but you're trying to use an AppController, which does not satisfy the interface.

The solution you probably want is to change controler := AppController{} to controler := &AppController{}

As cthom06 says, the answer is in the error.

The reason for the error message is that you have only implemented ResourceController when you are passing a pointer and not a value.

When you implemented Show, Create, etc., you used

func (self *AppController)...

This requires the method to get a pointer receiver, but AddResources is given the value of controler, not the pointer.

Here is some example code to show the problem:

package main

import "fmt"

type I interface {
	Show(i int)
}

type T struct{}

func (t *T) Show(i int) {
	fmt.Println(i)
}

func CallShow(i I) {
	i.Show(32);
}

func main() {
	obj := T{}
	
	// CallShow(obj) // This doesn't work unless you change func (t *T) to func (t T)
	CallShow(&obj) // This works because you pass a pointer
}

Also "ResourceHandler" is deprecated. I would recommend to use the v3 API:

api := rest.NewApi()
api.Use(rest.DefaultDevStack...)
router, err := rest.MakeRouter(
   // your routes here ...
)
if err != nil {
    log.Fatal(err)
}
api.SetApp(router)
log.Fatal(http.ListenAndServe(":8080", api.MakeHandler()))

Antoine - go-json-rest author