如何在Go中嵌套结构

Question

I'm working on structs, methods, and interfaces in Go, and am writing some code to test the concepts. I'm stuck on the following concept in an example I'm creating - some amplifiers have preamp tubes and power tubes. I thought I could define them in the amp struct using a generic tube struct, but of course it doesn't work the way I have it written, and when I research nested structs, they don't seem to be the applicable concept. How do I structure this so that "amp" has "preamptubes" and "powertubes", and those are each type "tube"?

type tube struct {
    model  string
    number int8
}

type amp struct {
    name         string
    model        string
    manufacturer string
    color        string
    knobs        int8
    switches     int8
    jacks        int8
    preamptubes  tube
    powertubes   tube
    ouputpower   int8
    fxloop       bool
}

**Edit: Update:** I should have including the error I was getting in the question. I rewrote the package this morning, and the preamptubes and powertubes types now work as expected. I suspect the problem was with how I was instantiating them in the main function. The following now works. This isn't production code, just an exercise to practice concepts. Thanks for helping me take a fresh look at it.

package main

import "fmt"

type tube struct {
    model  string
    number int8
}

type amp struct {
    name         string
    model        string
    manufacturer string
    color        string
    knobs        int8
    switches     int8
    jacks        int8
    preamptubes  tube
    powertubes   tube
    ouputpower   int8
    fxloop       bool
}

func main() {
    a := amp{
        name:         "MegaAmp",
        model:        "MA9000",
        manufacturer: "Amps R Us",
        color:        "blonde",
        knobs:        9,
        switches:     5,
        jacks:        6,
        preamptubes: tube{
            model:  "12AX7",
            number: 3},
        powertubes: tube{
            model:  "6V6",
            number: 4},
        fxloop: true}

    fmt.Println(a)
    fmt.Println(a.preamptubes.model)
}

Answer 1

I may be misunderstanding, but are you asking for a nested slice of structs? To accomplish this, simply use []tube:

package main

import "fmt"

type tube struct {
    model  string
    number int8
}

type amp struct {
    name         string
    model        string
    manufacturer string
    color        string
    knobs        int8
    switches     int8
    jacks        int8
    preamptubes  []tube
    powertubes   []tube
    ouputpower   int8
    fxloop       bool
}

func main() {
    v := amp{
        name:        "da amp",
        preamptubes: []tube{{model: "A"}},
        powertubes:  []tube{{model: "B"}},
    }

    fmt.Printf("%+v
", v)
}

https://play.golang.org/p/bPGHuEO40D0

Just a shot in the dark here, but you might also be running into import issues if your values exist in separate packages. Changing the first letter to an uppercase (ie, Tube, and AMP [see https://github.com/golang/go/wiki/CodeReviewComments#initialisms)) to access structs from different packages.