How to use switch statement in Go language?

Go language is an emerging programming language. It has the characteristics of efficiency, simplicity, security and concurrency, and is very suitable for use in fields such as web development, distributed systems and cloud computing. In the Go language, the switch statement is a very commonly used language structure, which can select different branches for execution based on the value of an expression. This article will introduce the basic usage and precautions of switch statements in Go language.

1. Basic Syntax

The switch statement in Go language is similar to the switch statement in other programming languages, but unlike other languages, the switch statement in Go language does not A break statement is required to prevent "fallthrough" (penetration effect). The following is a simple example:

func main() {
    num := 2
    switch num {
    case 1:
        fmt.Println("The number is 1")
    case 2:
        fmt.Println("The number is 2")
    case 3:
        fmt.Println("The number is 3")
    default:
        fmt.Println("Unknown number")
    }
}

In the above code, we first define a variable num equal to 2, and then match the value of this variable to select different branches for execution. Since the value of num is equal to 2, the second branch is selected and "The number is 2" is output. If the value of num is changed to 4, the default branch will be executed and "Unknown number" will be output.

2. Multi-condition matching

In actual programming, sometimes you need to match multiple values. You can use commas to separate multiple conditions to achieve this. Here is an example:

func main() {
    num := 3
    switch num {
    case 1, 2:
        fmt.Println("The number is 1 or 2")
    case 3, 4:
        fmt.Println("The number is 3 or 4")
    default:
        fmt.Println("Unknown number")
    }
}

In the above code, we use commas to separate multiple conditions to match different value ranges. If the value of num is 1 or 2, then the first branch will be executed and "The number is 1 or 2" will be output; if the value of num is 3 or 4, then the second branch will be executed and "The number is output" is 3 or 4".

3. Matching expressions

In some cases, it is necessary to use expressions to match conditions, not just the variable value itself. Here is an example:

func main() {
    num1 := 10
    num2 := 20
    switch {
    case num1 > num2:
        fmt.Println("num1 is greater than num2")
    case num2 > num1:
        fmt.Println("num2 is greater than num1")
    default:
        fmt.Println("num1 is equal to num2")
    }
}

In the above code, we did not specify the switch condition expression, but used a different expression in each case branch to match the condition. If the value of num1 is greater than num2, then the first branch will be executed and "num1 is greater than num2" will be output; if the value of num2 is greater than num1, then the second branch will be executed and "num2 is greater than num1" will be output; If the value of num1 is equal to num2, then the default branch will be executed and "num1 is equal to num2" will be output.

4. Type Switch

In addition to using expressions, you can also use types for matching. This type of switch is called a type switch. The following is an example:

func main() {
    var i interface{} = 10
    switch i.(type) {
    case int:
        fmt.Println("i is an integer")
    case float64:
        fmt.Println("i is a float")
    case bool:
        fmt.Println("i is a boolean")
    case string:
        fmt.Println("i is a string")
    default:
        fmt.Println("i is an unknown type")
    }
}

In the above code, we define an empty interface variable i and assign it to the integer 10. Then use a type switch to match the type of i and execute different branches based on different types. Since the type of i is int, the first branch will be executed and "i is an integer" will be output.

5. Notes

When using the switch statement, you need to pay attention to the following points:

• The switch statement can have no expression. In this case Expressions need to be used in case branches to match conditions.
• Different from other programming languages, the switch branch of the Go language does not automatically "fall through" (penetration effect), so there is no need to use a break statement to jump out of the switch branch.
• If there is no matching branch, no branch will be executed and no error will be reported.
• If you use the fallthrough statement to continue executing the next case branch after one case branch, you need to pay attention to avoid an infinite loop.

Summary:

The switch statement in Go language is a very commonly used language structure, which can select different branches for execution according to different conditions. When using switch statements, you need to pay attention to special cases such as multi-condition matching, using expressions to match conditions, type switch, etc. Proficient use of switch statements can help us write clearer, more efficient and safer code.

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