基于管道技术实现函数的流式调用

package main

import (
	"fmt"
	"log"
)

type user struct {
	name string //
	age  int    //
}

func filterAge(users []user) interface{} {
	var slice []user
	for _, user := range users {
		if user.age >= 18 && user.age <= 35 {
			slice = append(slice, user)
		}
	}
	return slice
}

func mapAgeToSlice(users []user) interface{} {
	var slice []int
	for _, user := range users {
		slice = append(slice, user.age)
	}
	return slice
}

func sumAge(users []user, pipes ...func([]user) interface{}) int {
	var ages []int
	var sum int
	for _, f := range pipes {
		result := f(users)
		switch result.(type) {
		case []user:
			users = result.([]user)
		case []int:
			ages = result.([]int)
		}
	}
	if len(ages) == 0 {
		log.Fatalln("mapAgeToSlice error")
	}
	for _, age := range ages {
		sum += age
	}
	return sum
}

func main() {
	var users = []user{
		{
			name: "张三",
			age:  18,
		},
		{
			name: "李四",
			age:  22,
		},
		{
			name: "王五",
			age:  20,
		},
		{
			name: "赵六",
			age:  -10,
		},
		{
			name: "孙七",
			age:  60,
		},
		{
			name: "周八",
			age:  10,
		},
	}
	sum := sumAge(users, filterAge, mapAgeToSlice)
	fmt.Println("用户年龄累加结果", sum)
}