go基础语法-条件语句

1.if else 语句

if语句后面的条件不需要括号

if n > 0 {
    return 1
}else {
    return -1
}

'if'之后，条件判断之前，可以初始化变量(作用域为整个if语句)，用';'分隔，类似其它语言的for语句

if m := 1 ; n > 0{
    return
}else {
    fmt.Println(m)
}

2.switch语句

golang中的switch，case语句无需写'break'

switch operator {
case "+":
	return a + b
case "-":
	return a - b
case "*":
	return a * b
case "/":
	return a / b
default:
	return a*a + b*b

'switch'后可以没有表达式，在case里面写条件

var grade string
switch {
case score < 0 || score > 100:
	grade = fmt.Sprintf("Wrong score : %d", score)
case score < 60:
	grade = "E"
case score < 70:
	grade = "D"
case score < 80:
	grade = "C"
case score < 90:
	grade = "B"
case score <= 100:
	grade = "A"
}
	return grade

测试代码

package main
import (
	"fmt"
	"io/ioutil"
)
/*
if else 测试
 */
func readFile() {
	const fileName = "a.txt"
	//go语言方法可以有多个返回值
	readBytes, err := ioutil.ReadFile(fileName)
	//普通写法
	if err != nil {
		fmt.Println(err)
	} else {
		fmt.Printf("%s\n", readBytes)
	}
	//类似for语句的写法
	if readBytes, err := ioutil.ReadFile(fileName); err != nil {
		fmt.Println(err)
	} else {
		fmt.Printf("%s\n", readBytes)
	}
}
/*
switch后有表达式
 */
func eval(a, b int, operator string) int {
	switch operator {
	case "+":
		return a + b
	case "-":
		return a - b
	case "*":
		return a * b
	case "/":
		return a / b
	default:
		panic("unsupported operator : " + operator) //panic中断程序运行并报错
	}
}
/*
switch后无表达式和default
 */
func grade(score int) string {
	var grade string
	switch {
	case score < 0 || score > 100:
		panic(fmt.Sprintf("Wrong score : %d", score))
		//grade = fmt.Sprintf("Wrong score : %d", score)
	case score < 60:
		grade = "E"
	case score < 70:
		grade = "D"
	case score < 80:
		grade = "C"
	case score < 90:
		grade = "B"
	case score <= 100:
		grade = "A"
	}
	return grade
}
func main() {
	readFile()
	fmt.Println(eval(1, 4, "+"))
	fmt.Println(grade(101))
}