[Yugong series] July 2022 go teaching course 018 switch of branch structure

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Preface

Switch In some computer languages, it is a reserved word , Its function is mostly to judge and choose . With Go language ,switch（ Switch statement ） Constant harmony case default Use it together .

One 、switch sentence

1.switch Basic use

Go In language switch Each of them case Are independent code blocks , There is no need to pass break Statement jumps out of the code block , To avoid execution to the next case Code block .

Related cases ：

package main

import "fmt"

func main() {
    
	num := 1

	switch num {
    
	case 1:
		fmt.Println(" Little fool ")
	case 2:
		fmt.Println(" Big fool ")
	default:
		fmt.Println(" Not Yugong ")
	}
}

In the above code ,case On integers num Judge , If the conditions meet , Then print the corresponding string . in addition , Also used. default Branch ,default Branch means if the conditions are not met , Then change the code block .

2. One branch, many values

package main

import "fmt"

func main() {
    
	num := 1

	switch num {
    
	case 1, 2:
		fmt.Println(" All fools ")
	}
}

3. Branch expressions

package main

import "fmt"

func main() {
    
	num := 1

	switch {
    
	case num > 0 && num < 2:
		fmt.Println(" Guess right, it's Yugong ")
	}
}

4.fallthrough keyword

Go In language swtich Statement case Are independent code blocks , After execution , Will not proceed to the next case,fallthrough You can continue to execute .

package main

import "fmt"

func main() {
    
	num := 1

	switch {
    
	case num > 0:
		fmt.Println(" Yugong No.1 ")
		fallthrough
	case num < 2:
		fmt.Println(" Yugong No. 2 ")
	}
}

Two 、 Related cases

1. Score your grades

package main

import "fmt"

func main() {
    
	// The examination result is greater than or equal to 90 Output A, Greater than or equal to 80 Output B, Greater than or equal to 70 Output C, Greater than or equal to 60 Output D, Fail output E
	var score float64
	fmt.Println(" Please enter the test scores :")
	fmt.Scan(&score)
	switch {
    
	case score >= 90:
		fmt.Println("A")
	case score >= 80:
		fmt.Println("B")
	case score >= 70:
		fmt.Println("C")
	case score >= 60:
		fmt.Println("D")
	default:
		fmt.Println("E")
	}
}

summary

• Some case After the following code is executed , Will not perform the following case, But out of the whole switch structure , It's equivalent to each case Followed by break( End ), But if we want to do something case after , Enforce the following case, have access to fallthrough.
• switch The structure and if Structure can be used in combination , It can be analyzed according to specific problems , Flexible to apply .