reflection2_7.go

func buildInStruct(ft reflect.Type) (reflect.Type, error) {
	if ft.NumIn() == 0 {
		return nil, errors.New("Must have at least one param")
	}
	var sf []reflect.StructField
	for i := 0; i < ft.NumIn(); i++ {
		ct := ft.In(i)
		if !ct.Comparable() {
			return nil, fmt.Errorf("parameter %d of type %s and kind %v is not comparable", i+1, ct.Name(), ct.Kind())
		}
		sf = append(sf, reflect.StructField{
			Name: fmt.Sprintf("F%d", i),
			Type: ct,
		})
	}
	s := reflect.StructOf(sf)
	return s, nil
}

func Cacher(f interface{}, expiration time.Duration) (interface{}, error) {
	ft := reflect.TypeOf(f)
	if ft.Kind() != reflect.Func {
		return nil, errors.New("Only for functions")
	}

	inType, err := buildInStruct(ft)
	if err != nil {
		return nil, err
	}

	if ft.NumOut() == 0 {
		return nil, errors.New("Must have at least one returned value")
	}

	fmt.Println("inType looks like", inType)
	return f, nil
}