What are the methods of exception handling in Go language?

The Go language has not supported exception handling mechanisms in the traditional sense, but in the Go language, there are some error handling methods that can be used to handle different error types. In this article, we will introduce exception handling methods in Go language.

1. Error return value

In the Go language, if the value returned by a function is an error type value, it means that some kind of error may occur in the function. When this function is called, the returned error value is checked to determine how the program should continue execution. This method is relatively direct and simple, and is the main error handling method in the Go language.

For example:

func Divide(a, b int) (int, error) {
    if b == 0 {
        return 0, fmt.Errorf("can't divide by zero")
    }
    return a / b, nil
}

It can be seen that if the divisor is 0, the function will return an error value. When this function is called, the return value is checked to see if an error has occurred. If the error value is not nil, the program executes the corresponding error handling code.

result, err := Divide(5, 0)
if err != nil {
    log.Fatal(err)
}

2. defer/panic/recover

Although the Go language does not have an exception handling mechanism in the traditional sense, it provides a combination of defer, panic and recover functions. Wrong way. This combination is called the "defer-panic-recover" mechanism.

• defer: This function calls a statement that needs to be executed before the current function ends. It can be any statement. They are generally used to release resources or manage the order of resources.
• panic: This function can immediately stop the current program execution. And starts passing an error value to the recover function at the highest level in the program's call stack. When the error value is not handled, the program will terminate.
• recover: This function is used to capture the error value passed at the bottom of the panic () function, then return the error, and stop the process of panic terminating the program early.

For example:

func Foo() {
    defer func() {
        if r := recover(); r != nil {
            log.Println("Recovered:", r)
        }
    }()
    panic("I'm panic!")
    fmt.Println("Continuing execution...")
}

As you can see, the panic function call is a way to terminate program execution. If there are multiple defer functions, they will be executed in FILO order, so the recover function should be placed in the outermost defer function.

3. Custom error types

Go language also provides a way to customize error types. When more fine-grained handling of specific errors is required, an error type can be customized.

For example:

type DivideError struct {
    dividend int
    divisor  int
}

func (de DivideError) Error() string {
    return fmt.Sprintf("can't divide %d by %d", de.dividend, de.divisor)
}

func Divide(a, b int) (int, error) {
    if b == 0 {
        return 0, DivideError{a, b}
    }
    return a / b, nil
}

In this example, we define a new error type DivideError. This type contains the divisor and dividend. This type also implements an Error method to return an error message. In our Divide function, if the divisor is 0, an initialized DivideError type is returned.

result, err := Divide(5, 0)
if de, ok := err.(DivideError); ok {
    log.Fatalf("Error handled by application: %s
", de.Error())
} else if err != nil {
    log.Fatal(err)
}

It should be noted that when using a custom type as an error, you need to use type assertions for type conversion in order to handle specific types of errors.

In this article, we introduce the methods of handling exceptions in the Go language, which are error return values, defer-panic-recover mechanism and custom error types. Of course, in actual development, the most appropriate exception handling method needs to be selected according to the specific situation.

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