在Go中将结构的字段和不同类型的值写入文件

Question

I'm writing a simple program that takes in input from a form, populates an instance of a struct with the received data and the writes this received data to a file.

I'm a bit stuck at the moment with figuring out the best way to iterate over the populated struct and write its contents to the file.

The struct in question contains 3 different types of fields (ints, strings, []strings).

I can iterate over them but I am unable to get their actual type.

Inspecting my posted code below with print statements reveals that each of their types is coming back as structs rather than the aforementioned string, int etc.

The desired output format is be plain text.

For example:

field_1="value_1"
field_2=10
field_3=["a", "b", "c"]

Anyone have any ideas? Perhaps I'm going about this the wrong way entirely?

func (c *Config) writeConfigToFile(file *os.File) {

    listVal := reflect.ValueOf(c)
    element := listVal.Elem()

    for i := 0; i < element.NumField(); i++ {
        field := element.Field(i)
        myType := reflect.TypeOf(field)

        if myType.Kind() == reflect.Int {
            file.Write(field.Bytes())
            } else {
                file.WriteString(field.String())
            }
        }
}

Answer 1

Instead of using the Bytes method on reflect.Value which does not work as you initially intended, you can use either the strconv package or the fmt to format you fields.

Here's an example using fmt:

var s string
switch fi.Kind() {
case reflect.String:
    s = fmt.Sprintf("%q", fi.String())
case reflect.Int:
    s = fmt.Sprintf("%d", fi.Int())
case reflect.Slice:
    if fi.Type().Elem().Kind() != reflect.String {
        continue
    }

    s = "["
    for j := 0; j < fi.Len(); j++ {
        s = fmt.Sprintf("%s%q, ", s, fi.Index(i).String()) 
    }
    s = strings.TrimRight(s, ", ") + "]"
default:
    continue
}

sf := rv.Type().Field(i)
if _, err := fmt.Fprintf(file, "%s=%s
", sf.Name, s); err!= nil {
    panic(err)
}

Playground: https://play.golang.org/p/KQF3CicVzA