golang echo controller model

Question

I am getting the following error when trying to factory my controller:

cannot use &(personController literal) (value of type *personController) as PersonController value in return statement: wrong type for method CreateNewPerson (have func(ctx github.com/labstack/echo/v4.Context) error, want func(ctx github.com/labstack/echo/v4.Context))

controller:

package controllers

import (
    "net/http"

    "github.com/labstack/echo/v4"
)

type personController struct{}

var (
// services
)

type PersonController interface {
    CreateNewPerson(ctx echo.Context)
    GetPerson(ctx echo.Context)
}

func NewPersonController() PersonController {
    return &personController{}
}

func (*personController) CreateNewPerson(ctx echo.Context) error {
    return ctx.JSON(http.StatusOK, "Hello")
}

func (*personController) GetPerson(ctx echo.Context) error {
    return ctx.JSON(http.StatusOK, "Hello")
}

and in my main func ai got this error :

func main() {
    e := echo.New()
    controller := controllers.NewPersonController()
    e.POST("/a", controller.CreateNewPerson)
}

cannot use controller.CreateNewPerson (value of type func(ctx echo.Contex

Why have both a personController struct and PersonController interface? — Hymns For Disco
– Hymns For Disco, Commented Apr 24, 2021 at 18:56
@HymnsForDisco I need to pass my mediator as a dependency and then I thought of creating the mediator in the struct of the controller this is bad ? Can you help me? — Ming
– Ming, Commented Apr 24, 2021 at 20:27
As a side note, returning an interface is an anti-pattern: medium.com/@cep21/… — Tyler Kropp
– Tyler Kropp, Commented Apr 24, 2021 at 22:14
@TylerKropptt From what I understand in the article is it better to return structs and use interfaces in the parameters? i'm new to go, i would be happy if u could give me an example. — Ming
– Ming, Commented Apr 24, 2021 at 22:33
Yes, that is a good general rule (though there could be exceptions). You can also read my answer about a similar idea here — Hymns For Disco
– Hymns For Disco, Commented Apr 25, 2021 at 10:54

Christian · Accepted Answer · 2021-04-24 17:30:08Z

1

Your interface and struct implementation don't match. If you want your interface method's to match what's required by the echo framework then do this:

type PersonController interface {
    CreateNewPerson(ctx echo.Context) error
    GetPerson(ctx echo.Context) error
}

answered Apr 24, 2021 at 17:30

Christian

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4 Comments

Ming Over a year ago

thank u, do you think this approach is better to have to instantiate a person controller to be able to call or just use a var without the interface? like this personController.new () personController.get ()

Christian Over a year ago

I would probably just keep them as pure functions (e.g. not a method on a struct) if they don't have any dependencies as it keeps things simple

Ming Over a year ago

they will have dependencies like commandbus and validator, but I'm a little confused on how to do this.

Christian Over a year ago

If that is the case I would have a struct which has these dependencies in it, the methods can then "hang off" the struct. This article goes through different patterns for organising DB connections alexedwards.net/blog/organising-database-access but the same logic could be applied to other resources. I would just get something working and see what works best for your use case 🚀

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