How Can Programmers Alphabetize Struct Field Output in Go?

Altering Print Output of Structs: Facilitating Alphabetical Field Arrangement

How can programmers generate structured data outputs by having fields appear in an alphabetical order? Specifically, consider the following:

type T struct {
    B int
    A int
}

t := &T{B: 2, A: 1}

doSomething(t)

fmt.Println(t)  // Desired output: &{1 2} — Fields sorted alphabetically

Solution via Field Ordering:

By default, structs preserve the declared field order. Thus, by redefining the struct with the desired field sequence, the output can be obtained:

type T struct {
    A int
    B int
}

Solution via Stringer Interface:

Another approach involves implementing the Stringer interface for the struct:

func (t T) String() string {
    return fmt.Sprintf("{%d %d}", t.A, t.B)
}

The fmt package checks for the Stringer implementation and utilizes its String() method for output generation.

Solution via Reflection:

For flexibility across structs, reflection can be utilized. Field names can be obtained, sorted, and their corresponding values retrieved.

func printFields(st interface{}) string {
    t := reflect.TypeOf(st)

    names := make([]string, t.NumField())
    for i := range names {
        names[i] = t.Field(i).Name
    }
    sort.Strings(names)

    v := reflect.ValueOf(st)
    buf := &bytes.Buffer{}
    buf.WriteString("{")
    for i, name := range names {
        val := v.FieldByName(name)
        if !val.CanInterface() {
            continue
        }
        if i > 0 {
            buf.WriteString(" ")
        }
        fmt.Fprintf(buf, "%v", val.Interface())
    }
    buf.WriteString("}")

    return buf.String()
}

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