walkstruct.go

package walkstruct

import (
	"fmt"
	"reflect"
	"unicode"
)

// WalkStruct walks the exported fields of a struct using reflection,
// and calls fn for each field.
func WalkStruct(s interface{}, fn func(reflect.StructField, reflect.Value)) {
	t := reflect.TypeOf(s)
	v := reflect.ValueOf(s)
	if v.Kind() == reflect.Ptr {
		v = v.Elem()
		t = t.Elem()
	}
	if v.Kind() != reflect.Struct {
		panic(fmt.Sprintf("WalkStruct: s is not struct: %T", s))
	}
	for i := 0; i < v.NumField(); i++ {
		ft := t.Field(i)
		if !exportedField(ft) {
			continue
		}
		fn(ft, v.Field(i))
	}
}

func exportedField(f reflect.StructField) bool {
	return !f.Anonymous && unicode.IsUpper(rune(f.Name[0]))
}

// StructFields returns the names of all exported fields of struct s.
func StructFields(s interface{}, tag string) []string {
	var f []string
	WalkStruct(s, func(ft reflect.StructField, fv reflect.Value) {
		n := ft.Tag.Get(tag)
		if n == "" {
			n = ft.Name
		}
		f = append(f, n)
	})
	return f
}

// StructValues returns the values of all exported fields of struct s.
func StructValues(s interface{}) []interface{} {
	var v []interface{}
	WalkStruct(s, func(ft reflect.StructField, fv reflect.Value) {
		v = append(v, fv.Interface())
	})
	return v
}

// StructValuesAddr returns pointer values of all exported fields of struct s.
func StructValuesAddr(s interface{}) []interface{} {
	var v []interface{}
	WalkStruct(s, func(ft reflect.StructField, fv reflect.Value) {
		// this will panic if !fv.CanAddr(); and it should
		v = append(v, fv.Addr().Interface())
	})
	return v
}