self-referential functions practice

self_referential_functions.go

package main

import "fmt"

type Cat struct {
	Name string
	Age  int
}

type catOpt func(c *Cat) catOpt

func (c *Cat) Options(opts ...catOpt) []catOpt {
	var prevOpts []catOpt
	for _,opt := range opts {
		prevOpts = append(prevOpts, opt(c))
	}
	return prevOpts
}

func SetName(name string) catOpt {
	return func(c *Cat) catOpt {
		prev := c.Name
		c.Name = name
		return SetName(prev)
	}
}

func SetAge(age int) catOpt {
	return func(c *Cat) catOpt {
		prev := c.Age
		c.Age = age
		return SetAge(prev)
	}
}

func main() {
	cat := &Cat{Name: "hana",Age: 1}
	fmt.Printf("%+v\n",cat) //&{Name:hana Age:1}
	f(cat)
	fmt.Printf("%+v\n",cat) //&{Name:hana Age:1}
	f2(cat)
	fmt.Printf("%+v\n\n",cat) //&{Name:hana Age:1}
}

func f(cat *Cat) {
	prev := cat.Options(SetName("kinako"))
	defer cat.Options(prev...)
	fmt.Printf("%+v\n",cat) //&{Name:kinako Age:1}
}

func f2(cat *Cat) {
	prev := cat.Options(SetName("mike"),SetAge(2))
	fmt.Printf("%+v\n",cat) //&{Name:mike Age:2}
	prev2 :=  cat.Options(prev...)
	fmt.Printf("%+v\n",cat) //&{Name:hana Age:1}
	prev3 :=  cat.Options(prev2...)
	fmt.Printf("%+v\n",cat) //&{Name:mike Age:2}
	defer cat.Options(prev3...)
}

error

func SetAge(age int) catOpt {
	return func(c *Cat) catOpt {
		prev := c.Age
		c.Age = age
		fmt.Printf("loop: %+v\n",c)
		return SetAge(prev)(c)
	}
}