CODEWITHSUNDEEP
structreferencegoslice
jordan2175
jordan2175

Reputation: 938

Golang problems with referencing arrays of sub structures

I am having a problem figuring out how to reference elements of a sub structure.

See: http://play.golang.org/p/pamS_ZY01s

Given something like following.... How do you reference data in the room struct? I have tried fmt.Println(*n.Homes[0].Rooms[0].Size), but that does not work.

Begin Code example

package main

import (
    "fmt"
)

type Neighborhood struct {
    Name  string
    Homes *[]Home
}

type Home struct {
    Color string
    Rooms *[]Room
}

type Room struct {
    Size string
}

func main() {
    var n Neighborhood
    var h1 Home
    var r1 Room

    n.Name = "Mountain Village"
    h1.Color = "Blue"
    r1.Size = "200 sq feet"

    // Initiaize Array of Homes
    homeslice := make([]Home, 0)
    n.Homes = &homeslice

    roomslice := make([]Room, 0)
    h1.Rooms = &roomslice

    *h1.Rooms = append(*h1.Rooms, r1)
    *n.Homes = append(*n.Homes, h1)

    fmt.Println(n)
    fmt.Println(*n.Homes)

}

Upvotes: 0

Views: 151

Answers (1)

Toni Cárdenas
Toni Cárdenas

Reputation: 6848

First, *[]Home is really wasteful. A slice is a three worded struct under the hood, one of them being itself a pointer to an array. You are introducing a double indirection there. This article on data structures in Go is very useful.

Now, because of this indirection, you need to put the dereference operator * in every pointer-to-slice expression. Like this:

fmt.Println((*(*n.Homes)[0].Rooms)[0].Size)

But, really, just take out the pointers.

Upvotes: 4

Related Questions