Initializing a struct in a struct

Question

This is a slight twist on similar posts.

I have a package called data that has the following:

type CityCoords struct {
    Name string
    Lat float64
    Long float64
}

type Country struct {
        Name string
        Capitol *CityCoords
}

In my main function I try initializing a Country like so:

germany := data.Country {
    Name: "Germany",
    Capitol: {
        Name: "Berlin", //error is on this line
        Lat: 52.5200,
        Long: 13.4050,
    },

}

When I build my project, I get this error aligned with the "Name" attributed as I've flagged above:

missing type in composite literal

How do I resolve this error?

Answer 1

As far as know, * means that an object pointer is expected. So, you could initiate it first using &;

func main() {
    germany := &data.Country{
        Name: "Germany",
        Capitol: &data.CityCoords{
            Name: "Berlin", //error is on this line
            Lat: 52.5200,
            Long: 13.4050,
        },
    }
    fmt.Printf("%#v\n", germany)
}

Or, you can prefer a more elegant way;

// data.go
package data

type Country struct {
    Name    string
    Capital *CountryCapital
}

type CountryCapital struct {
    Name    string
    Lat     float64
    Lon     float64
}

func NewCountry(name string, capital *CountryCapital) *Country {
    // note: all properties must be in the same range
    return &Country{name, capital}
}

func NewCountryCapital(name string, lat, lon float64) *CountryCapital {
    // note: all properties must be in the same range
    return &CountryCapital{name, lat, lon}
}

// main.go
func main() {
    c := data.NewCountry("Germany", data.NewCountryCapital("Berlin", 52.5200, 13.4050))
    fmt.Printf("%#v\n", c)
}