go数字和字符串转换及方法返回值

package main

import (
	"fmt"
	"strconv"
)


//const 来定义枚举类型
const (
	//可以在const() 添加一个关键字 iota， 每行的iota都会累加1, 第一行的iota的默认值是0
	BEIJING = iota	 //iota = 0
	SHANGHAI 		  //iota = 1
	SHENZHEN          //iota = 2
)

const (
	a, b = iota+1, iota+2 // iota = 0, a = iota + 1, b = iota + 2, a = 1, b = 2
	c, d				  // iota = 1, c = iota + 1, d = iota + 2, c = 2, d = 3
	e, f				  // iota = 2, e = iota + 1, f = iota + 2, e = 3, f = 4

	g, h = iota * 2, iota *3  // iota = 3, g = iota * 2, h = iota * 3, g = 6, h = 9 
	i, k					   // iota = 4, i = iota * 2, k = iota * 3 , i = 8, k = 12
)


func fun1(a string, b int) int {
	fmt.Println("a = ", a)
	fmt.Println("b = ", b)
	b,error := strconv.Atoi(a)
	if error != nil{
	fmt.Println("字符串转换成整数失败")
	}
	b = b + 1
	fmt.Println(b)
	return b
}

//返回多个返回值，匿名的
func fun2(a int, b string) (string, int) {
	fmt.Println("a = ", a)
	fmt.Println("b = ", b)
	d := strconv.Itoa(a)   //数字变成字符串
	d = d + "sdfs"
	fmt.Println(d)

	e,error := strconv.Atoi(b)  //字符串转换成整数
	if error != nil{
		fmt.Println("字符串转换成整数失败")
		} else {
		fmt.Println(e)
	}
	return d, e
}

//返回多个返回值， 有形参名称的
func fun3(a string, b int) (r1 string, r2 int) {
	fmt.Println("---- foo3 ----")
	fmt.Println("a = ", a)
	fmt.Println("b = ", b)

	//r1 r2 属于foo3的形参，  初始化默认的值是0
	//r1 r2 作用域空间 是foo3 整个函数体的{}空间
	fmt.Println("r1 = ", r1)
	fmt.Println("r2 = ", r2)

	//给有名称的返回值变量赋值
	r1 = a
	r2 = 2000

	return
}


func main() {
	//常量(只读属性)
	const length int = 10

	fmt.Println("length = ", length)

	//length = 100 //常量是不允许修改的。
	fmt.Println("BEIJIGN = ", BEIJING)
	fmt.Println("SHANGHAI = ", SHANGHAI)
	fmt.Println("SHENZHEN = ", SHENZHEN)

	fmt.Println("a = ", a, "b = ", b)
	fmt.Println("c = ", c, "d = ", d)
	fmt.Println("e = ", e, "f = ", f)
	fmt.Println("g = ", g, "h = ", h)
	fmt.Println("i = ", i, "k = ", k)

	// iota 只能够配合const() 一起使用， iota只有在const进行累加效果。

	c := fun1("666", 555)
	fmt.Println("c = ", c)

	ret1, ret2 := fun2(1000, "999")
	fmt.Println("ret1 = ", ret1, " ret2 = ", ret2)

	ret1, ret2 = fun3("foo3", 333)
	fmt.Println("ret1 = ", ret1, " ret2 = ", ret2)


}