Question

Can a Go struct inherit a set of values from a type of another struct?

Something like this.

type Foo struct {
    Val1, Val2, Val3 int
}

var f *Foo = &Foo{123, 234, 354}

type Bar struct {
    // somehow add the f here so that it will be used in "Bar" inheritance
    OtherVal string
}

Which would let me do this.

b := Bar{"test"}
fmt.Println(b.Val2) // 234

If not, what technique could be used to achieve something similar?

Answer 1

Here’s how you may embed the Foo struct in the Bar one :

type Foo struct {
    Val1, Val2, Val3 int
}
type Bar struct {
    Foo
    OtherVal string
}
func main() {
    f := &Foo{123, 234, 354}
    b := &Bar{*f, "test"}
    fmt.Println(b.Val2) // prints 234
    f.Val2 = 567
    fmt.Println(b.Val2) // still 234
}

Now suppose you don’t want the values to be copied and that you want b to change if f changes. Then you don’t want embedding but composition with a pointer :

type Foo struct {
    Val1, Val2, Val3 int
}
type Bar struct {
    *Foo
    OtherVal string
}
func main() {
    f := &Foo{123, 234, 354}
    b := &Bar{f, "test"}
    fmt.Println(b.Val2) // 234
    f.Val2 = 567
    fmt.Println(b.Val2) // 567
}

Two different kind of composition, with different abilities.