golang error catching

In golang, errors are inevitable. No matter how small or large your application is, you will encounter errors. Therefore, it is very important to understand how to catch and handle errors correctly. This article will explore the error handling mechanism and some best practices in golang.

Error type

In golang, error is a type that implements the error interface. This interface has only one method: Error() string, which returns a string describing the error. Since the error interface is a predefined interface, we cannot add additional methods to it.

The following is a simple golang error example:

func divide(a, b int) (int, error) {
    if b == 0 {
        return 0, errors.New("division by zero")
    }
    return a / b, nil
}

func main() {
    result, err := divide(10, 2)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(result) // 5

    result, err = divide(10, 0)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(result) // not executed, log.Fatal will exit the program
}

In this example, we define a function named divide which divides two integers . If the second parameter is 0, an error object containing a descriptive string is returned. In the main function, we call the divide function twice, the first time successfully calculates and prints the result, while the second time throws an error due to division by 0 and uses log.Fatal Call the exit procedure.

Error handling mechanism

Golang provides some built-in functions to capture and handle errors. The following are some commonly used functions:

1. errors.New(str string) error

This function accepts a string parameter and returns an implementation The object of the error interface. Example: return 0, errors.New("division by zero").

2. fmt.Errorf(format string, a ...interface{}) error

This function is the same as fmt.PrintfSimilarly, accepts a formatted string and variable parameters, and returns an object that implements the error interface. Example: return nil, fmt.Errorf("invalid argument: %d", num).

3. log.Fatal(v ...interface{})

This function accepts variable parameters and prints the message using os.Exit(1)End the program. Typically used to exit a program when a fatal error occurs. Example: log.Fatal("fatal error: ", err).

4. panic(v interface{})

This function accepts a value of any type and will be thrown when the program encounters a serious problem panic. You need to be careful when using it in a program because it will interrupt the normal execution of the program and may cause data loss and other problems.

The recover() function can capture the thrown panic and return its value.

Best Practices

In golang, it is very important to handle errors correctly. Here are some best practices:

1. Don’t ignore errors

Ignoring errors is a common error handling problem. In golang, if you don't check the errors returned by the function and try to continue the program execution without errors, then the program will crash or lose data at some point.

2. Returning errors in functions

When an error is encountered, we should return the error object in the function instead of printing the error message or calling ## directly in the function #log.Fatal. This way the caller of the function can handle the error appropriately depending on the situation. At the same time, we should use appropriate error messages to describe the problem.

Handling errors in multiple function calls

defer statement to clean up any resources before processing the return value of the function. This way we can handle errors in only one place and the code is cleaner.

func main() {
    file, err := os.Open("myfile.txt")
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()

    reader := bufio.NewReader(file)
    line, err := reader.ReadString('
')
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(line)
}

defer statement to close the file handle after opening the file correctly. While reading the file we checked again for errors.

Include additional information when logging

log package to log, we should include additional information related to the error, For example, function name, file name, line number, etc. This makes the logs more useful and helps locate errors quickly.

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