Extract tags from Go struct as a reflect.Value

Question

I'm trying to extract tags from a certain Value which is a struct. I am able to get the fields of the struct but unable to extract the tags. What am I doing wrong here? I've tried many different ways (using reflect.Type, interface{} etc) but all failed.

type House struct {
    Room string
    Humans Human
}

type Human struct {
    Name         string `anonymize:"true"` // Unable to get this tag
    Body         string
    Tail         string `anonymize:"true"` // Unable to get this tag
}

func printStructTags(f reflect.Value) { // f is of struct type `human`
    for i := 0; i < f.NumField(); i++ {
        fmt.Printf("Tags are %s\n", reflect.TypeOf(f).Field(i).Tag) // TAGS AREN'T PRINTED
    }
}

The reason I use reflect.Value as the parameter is because this function is called from another function in the following manner

    var payload interface{}
    payload = &House{}
    // Setup complete
    v := reflect.ValueOf(payload).Elem()
    for j := 0; j < v.NumField(); j++ { // Go through all fields of payload
        f := v.Field(j)
        if f.Kind().String() == "struct" { 
            printStructTags(f)
        }
    }

Any insights would be extremely valuable

Answer 1

When you call reflect.TypeOf(f) you get the type of f, which is already a reflect.Value.

Use the Type() func of this f to get the type and do the Field check on it:

func printStructTags(f reflect.Value) { // f is of struct type `human`
    for i := 0; i < f.NumField(); i++ {
        fmt.Printf("Tags are %s\n", f.Type().Field(i).Tag) 
    }
}

However, it's easier to check for a tag and get its value with f.Type().Field(i).Tag.Get("anonymize"). This way you directly get the assigned value, for example true in your case and an empty string if the tag doesn't exist.