自定义结构中的指针

Question

Recently, I got exposed to following source code from "Go Programming Blueprints" book.

type googleGeometry stuct {
    *googleLocation `json:"location"`
}
type googleLocation struct {
    Lat float64 `json:"lat"`
    Lng float64 `json:"lng"`
}

What I don't understand is why googleGeometry structure uses pointer instead of literal, and what is the reason behind such declaration?

I would expect below declaration instead of a pointer.

type googleGeometry stuct {
    gl googleLocation `json:"location"`
}

Answer 1

googleGeometry embeds a pointer to a googleLocation. It is essentially an unnamed field so that the Lat and Lng fields are accessible as if they were top level fields.

Why use

type googleGeometry stuct {
    *googleLocation `json:"location"`
}

instead of

type googleGeometry stuct {
    googleLocation `json:"location"`
}

?

I think they made the wrong call here. The pointer is nillable so if you do:

g := googleGeometry{}
fmt.Println(g.Lat)

you will get a nil reference panic. If you embed a non-pointer struct, the fields will be automatically initialized to zeros.