用作函数参数的任意结构片的接口（golang）

Question

I have two different types of structs in my app.

I'll show it as a simplified example:

type typeA struct {
    fieldA1 int
    fieldA2 string
}

type typeB struct {
    fieldB1 float32
    fieldB2 bool
}

First I init slices of them, then I want to store them in DB.

a := []typeA{
    {10, "foo"},
    {20, "boo"},
}
b := []typeB{
    {2.5, true},
    {3.5, false},
}

My first attempt was to iterate over first slice, then over second slice. It works just fine, but doesn't look DRY. The code is clearly duplicated:

printBothArrays(a, b)

// ...

func printBothArrays(dataA []typeA, dataB []typeB) {
    // Not DRY
    for i, row := range dataA {
        fmt.Printf("printBothArrays A row %d: %v
", i, row)
    }
    for i, row := range dataB {
        fmt.Printf("printBothArrays B row %d: %v
", i, row)
    }
}

A wrong way to make it DRY is to split it into 2 functions:

printArrayA(a)
printArrayB(b)

// ...

func printArrayA(data []typeA) {
    // Not DRY too, because the code is just split between 2 funcs
    for i, row := range data {
        fmt.Printf("printArrayA row %d: %v
", i, row)
    }
}

func printArrayB(data []typeB) {
    // Not DRY too, because the code is just split between 2 funcs
    for i, row := range data {
        fmt.Printf("printArrayB row %d: %v
", i, row)
    }
}

These two functions' signatures are different, but the code is just the same!

I thought of an universal function which can take any []struct and just store it. As my store function can take any interface{}, I thought of this:

func printArrayAny(data [](interface{})) {
    for i, row := range data {
        fmt.Printf("printArrayAny row %d: %v
", i, row)
    }
}

But I've tried different ways and I can't match any shared interface. I'm getting errors like:

cannot use a (type []typeA) as type []interface {} in argument to printArrayAny

I don't really want to make any heavy lifting like converting it to []map[string]interface, or using reflect, as both slices are really big.

Is there a way to modify printArrayAny so it can receive and iterate over any arbitrary []struct ?

Go playground link: https://play.golang.org/p/qHzcQNUtLIX

Answer 1

Use the reflect package to iterate over arbitrary slice types:

func printArrayAny(data interface{}) {
    v := reflect.ValueOf(data)
    for i := 0; i < v.Len(); i++ {
        fmt.Printf("printArrayAny row %d: %v
", i, v.Index(i).Interface())
    }
}

Playground Example.