ICode9

精准搜索请尝试: 精确搜索
首页 > 其他分享> 文章详细

[Go] switch - fallthrough

2022-09-04 16:32:03  阅读:194  来源: 互联网

标签:case less fallthrough fmt Println switch Go than


fallthrough keyword is used in switch statement in golang. This keyword is used in switch case block. If the fallthrough keyword is present in the case block, then it will transfer control to the next case even though the current case might have matched.

package main

import "fmt"

func main() {
    i := 45

    switch {
    case i < 10:
        fmt.Println("i is less than 10")
    case i < 50:
        fmt.Println("i is less than 50")
    case i < 100:
        fmt.Println("i is less than 100")
    }
}

 

Output:

i is less than 50

 

By default the switch statement matches goes through all the case statement from top to bottom and tries to find the first case expression that matches the switch expression. Once the matching case is found, it exits  and does not consider the other cases. This is what is happening in above example. Even though i is less than 100 but that case is never executed because the second case is matched and after that it exits

fallthrough keyword allows way around this limitation. See below code for fallthrough keyword example. In below example even though the second case matched it went through the third case because of fallthrough keyword

ackage main

import "fmt"

func main() {
    i := 45
    switch {
    case i < 10:
        fmt.Println("i is less than 10")
        fallthrough
    case i < 50:
        fmt.Println("i is less than 50")
        fallthrough
    case i < 100:
        fmt.Println("i is less than 100")
    }
}

 

Output:

i is less than 50
i is less than 100

 

fallthrough needs to be final statement within the switch block. If it is not then compiler raise error

fallthrough statement out of place
package main

import "fmt"

func main() {
    i := 45
    switch {
    case i < 10:
        fmt.Println("i is less than 10")
        fallthrough
    case i < 50:
        fmt.Println("i is less than 50")
        fallthrough
        fmt.Println("Not allowed") // ERROR
    case i < 100:
        fmt.Println("i is less than 100")
    }
}

error as we have fmt.Println after the fallthrough statement

 

[Notice] be careful when use fallthrough, it seems that fallthrough will enter next case block no matter the condition. That might cause suprise bug in code;

func main() {
	i := 45
	switch {
	case i < 10:
		fmt.Println("i is less than 10")
		fallthrough
	case i < 50:
		fmt.Println("i is less than 50")
		fallthrough
	case i < 20:
		fmt.Println("i is less than 20")
	}
}

// i is less than 50
// i is less than 20

 

标签:case,less,fallthrough,fmt,Println,switch,Go,than
来源: https://www.cnblogs.com/Answer1215/p/16655347.html

本站声明: 1. iCode9 技术分享网(下文简称本站)提供的所有内容,仅供技术学习、探讨和分享;
2. 关于本站的所有留言、评论、转载及引用,纯属内容发起人的个人观点,与本站观点和立场无关;
3. 关于本站的所有言论和文字,纯属内容发起人的个人观点,与本站观点和立场无关;
4. 本站文章均是网友提供,不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属;如您发现该文章侵犯了您的权益,可联系我们第一时间进行删除;
5. 本站为非盈利性的个人网站,所有内容不会用来进行牟利,也不会利用任何形式的广告来间接获益,纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。

专注分享技术,共同学习,共同进步。侵权联系[81616952@qq.com]

Copyright (C)ICode9.com, All Rights Reserved.

ICode9版权所有