如何在以下代码中实现接口？

Question

I have the following code and I want to use interfaces:

Current code:

import (        
    "github.com/dorzheh/deployer/ui/dialog_ui"
    . "github.com/dorzheh/go-dialog"
)

// all methods in https://github.com/dorzheh/deployer/blob/master/ui/dialog_ui/dialog_ui.go#L28
type Pb struct {
    sleep time.Duration
    step  int
}

type DialogUi struct {
    *Dialog //The source is https://github.com/dorzheh/go-dialog/blob/master/dialog.go#L34
    Pb *Pb
}

I am trying to implement interfaces this way:

import (
    "testing"
    // . "github.com/dorzheh/go-dialog"
    //"github.com/dorzheh/deployer/ui/dialog_ui"
)


type PBifaceT interface {
    Step() int
}

type TestDialogUiT struct {
    Pb *PBifaceT
}

func TestUiValidateUser(t *testing.T) {
    x := dialog_ui.TestDialogUiT{}
    PbPb := ImplPBifaceT{}
    x.Pb = PbPb

    parentId := x.Pb.Step()
    t.Logf(fmt.Sprintf("%v", parentId))
}

I've made a playground. As you can see it runs in the following error:

prog.go:23: cannot use PbPb (type ImplPBifaceT) as type *PBifaceT in assignment:
    *PBifaceT is pointer to interface, not interface
prog.go:25: x.Pb.Step undefined (type *PBifaceT is pointer to interface, not interface)

I tried to convert them in this playground:

func NewD() *PBifaceT {
    // var err error
    var res =new(ImplPBifaceT)
    return (*PBifaceT)(res)
}

func main() {
    x := TestDialogUiT{}
    x.Pb = NewD()
    parentId := x.Pb.Step()
    fmt.Sprintf("%v", parentId)

}

The issue:

prog.go:23: cannot convert res (type *ImplPBifaceT) to type *PBifaceT
prog.go:30: x.Pb.Step undefined (type *PBifaceT is pointer to interface, not interface)

Answer 1

Do not use pointer to interface unless you are sure that's what you want, see Pb *PBifaceT inside TestDialogUiT. If you change it to just Pb PBifaceT your playground link just works.

An interface is already a pointer.