Initialize a nested struct in Golang

Question

I cannot figure out how to initialize a nested struct. Find an example here: http://play.golang.org/p/NL6VXdHrjh

package main

type Configuration struct {
    Val   string
    Proxy struct {
        Address string
        Port    string
    }
}

func main() {

    c := &Configuration{
        Val: "test",
        Proxy: {
            Address: "addr",
            Port:    "80",
        },
    }

}

Answer 1

If you don't want to go with separate struct definition for nested struct and you don't like second method suggested by @OneOfOne you can use this third method:

package main
import "fmt"
type Configuration struct {
    Val   string
    Proxy struct {
        Address string
        Port    string
    }
}

func main() {
    c := &Configuration{
        Val: "test",
    }

    c.Proxy.Address = `127.0.0.1`
    c.Proxy.Port = `8080`
}

You can check it here: https://play.golang.org/p/WoSYCxzCF2

Answer 2

Define your Proxy struct separately, outside of Configuration, like this:

type Proxy struct {
    Address string
    Port    string
}

type Configuration struct {
    Val string
    P   Proxy
}

c := &Configuration{
    Val: "test",
    P: Proxy{
        Address: "addr",
        Port:    "80",
    },
}

See http://play.golang.org/p/7PELCVsQIc

Answer 3

You need to redefine the unnamed struct during &Configuration{}

package main

import "fmt"

type Configuration struct {
    Val   string
    Proxy struct {
        Address string
        Port    string
    }
}

func main() {

    c := &Configuration{
        Val: "test",
        Proxy: struct {
            Address string
            Port    string
        }{
            Address: "127.0.0.1",
            Port:    "8080",
        },
    }
    fmt.Println(c)
}

https://play.golang.org/p/Fv5QYylFGAY

Answer 4

You can define a struct and create its object in another struct like i have done below:

package main

import "fmt"

type Address struct {
    streetNumber int
    streetName   string
    zipCode      int
}

type Person struct {
    name    string
    age     int
    address Address
}

func main() {
    var p Person
    p.name = "Vipin"
    p.age = 30
    p.address = Address{
        streetName:   "Krishna Pura",
        streetNumber: 14,
        zipCode:      475110,
    }
    fmt.Println("Name: ", p.name)
    fmt.Println("Age: ", p.age)
    fmt.Println("StreetName: ", p.address.streetName)
    fmt.Println("StreeNumber: ", p.address.streetNumber)
}

Hope it helped you :)

Answer 5

You have this option also:

type Configuration struct {
        Val string
        Proxy
}

type Proxy struct {
        Address string
        Port    string
}

func main() {
        c := &Configuration{"test", Proxy{"addr", "port"}}
        fmt.Println(c)
}

Answer 6

Well, any specific reason to not make Proxy its own struct?

Anyway you have 2 options:

The proper way, simply move proxy to its own struct, for example:

type Configuration struct {
    Val string
    Proxy
}

type Proxy struct {
    Address string
    Port    string
}

func main() {

    c := &Configuration{
        Val: "test",
        Proxy: Proxy{
            Address: "addr",
            Port:    "port",
        },
    }
    fmt.Println(c)
}

The less proper and ugly way but still works:

c := &Configuration{
    Val: "test",
    Proxy: struct {
        Address string
        Port    string
    }{
        Address: "addr",
        Port:    "80",
    },
}