Golang多个if 优化与代码健壮性小技巧

没优化之前: 嵌套if, 检查是否有中文字段值, 否则去查找英文值, 都没有则返回默认值

if record.City.Names["zh-CN"] == "" {
	city = record.City.Names["en"]
	if record.City.Names["en"] == "" {
		city = record.City.Names["en"]
	}
} else {
	city = "未知地域"
}

优化后: 平级if...else代替嵌套if

if name, ok := record.City.Names["zh-CN"]; ok {
	city = name
} else if city, ok = record.City.Names["en"]; ok {
	city = record.City.Names["en"]
} else {
	city = "未知地域"
}

知识点: 利用go的ok模式,对查询map对象的值是否存在更加简洁和安全

更进一步的优化, 去掉else

这对else的处理逻辑有明确的值时非常有用

city = "未知地域"
if name, ok := record.City.Names["zh-CN"]; ok {
	city = name
} else if name, ok = record.City.Names["en"]; ok {
	city = name
}

使用switch代替多个if分支: 根据成绩的分数段给出对应的等级

func calculateGrade(score int) string {
	var grade string

	if score >= 90 && score = 80 && score = 70 && score = 60 && score = 0 && score < 60 {
		grade = "F"
	} else {
		grade = "Invalid Score"
	}

	return grade
}

优化后: 使代码更加简洁，并且避免了多个嵌套的 if-else 语句。同时，使用 switch 语句还能够处理默认情况，即当 score 不满足任何一个分支条件时，默认返回 "Invalid Score"

func calculateGrade(score int) string {
	var grade string

	switch {
	case score >= 90 && score = 80 && score = 70 && score = 60 && score = 0 && score < 60:
		grade = "F"
	default:
		grade = "Invalid Score"
	}

	return grade
}

错误检查

首先看etcdgithub官网的错误处理例子:

resp, err := cli.Put(ctx, "", "")
if err != nil {
	switch err {
	case context.Canceled:
		log.Fatalf("ctx is canceled by another routine: %v", err)
	case context.DeadlineExceeded:
		log.Fatalf("ctx is attached with a deadline is exceeded: %v", err)
	case rpctypes.ErrEmptyKey:
		log.Fatalf("client-side error: %v", err)
	default:
		log.Fatalf("bad cluster endpoints, which are not etcd servers: %v", err)
	}
}

我们可以进一步优化, 使用go自带的包errors对错误类型进行更加健壮的检查, 但是对开发者的要求较高, 需要预定义正确的错误类型, 来保证正确的比较错误

resp, err := cli.Put(ctx, "", "")
if err2 != nil {
		switch {
		case errors.Is(err, context.Canceled):
			log.Fatalf("ctx is canceled by another routine: %v", err)
		case errors.Is(err, context.DeadlineExceeded):
			log.Fatalf("ctx is attached with a deadline is exceeded: %v", err)
		case errors.Is(err, rpctypes.ErrEmptyKey):
			log.Fatalf("client-side error: %v", err)
		default:
			log.Fatalf("bad cluster endpoints, which are not etcd servers: %v", err)
		}
	}