Interface Fields

[Dave Protasowski]

I'm doing some due-diligence and wondering if there's any old topics about extending interfaces to support field sets.

ie.

type WithID interface {

   ID string

}

type X struct { ID string }

type Y struct { ID string }

func PrintID(item WithID) {

  fmt.Println(item.ID)

}

In the above the PrintID function only accepts structs with a field named `ID` - which X & Y satisfy. This is sort of like duck typing but with fields.

I've found https://groups.google.com/g/golang-nuts/c/18gH5TR_3ZE/m/9dyyT4veBgAJ but I don't know the discussion the person was referencing and it seems specific to generics.

thanks,

dave

[Henry]

I remember reading some proposals about it somewhere, either here at golang-nuts or at github. The general consensus was no, because interface is all about behavior. Struct is for data and interface is for behavior, or something like that if I remember it correctly. 

In your specific example, since PrintID requires only the ID field, you can refactor it into something like this:

```

func Print(str string) {

   fmt.Println(id)

}

Print(x.ID) 

Print(y.ID)

```
I hope it helps.

Henry

[Dave Protasowski]

Found https://github.com/golang/go/issues/23796

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