polymorphism.go

import "fmt"

type Other struct {
    c bool
    x, y int
}

type Model interface{}

type A struct {
    x int
}

type B struct {
    A
    y int
}

func NewModel(other *Other) Model {
    if other.c {
        return &A{x: other.x,}
    } else {
        return &B{
            A: A{x: other.x,},
            y: other.y,
        }
    }
}

func test(model Model) {
    if a, ok := model.(*A); ok {
        fmt.Printf("x: %v", a.x)
    } else {
        b := model.(*B)
        fmt.Printf("x: %v, y: %v", b.x, b.y)
    }
}