Error handling mechanism in Go language

As a modern programming language, the Go language has good support for the error handling mechanism. Its error handling ideas are clear and simple. It not only provides standard error handling methods, but also supports custom error types to facilitate developers. More flexible error handling.

1. Overview of Error Handling

In the Go language, error handling is regarded as a normal return value, which is easy to understand. The recommended way in Go is for the function to return an error value. If the call is successful, it returns a nil value. Otherwise, it returns a non-null error value, usually a type that implements the Error interface.

Go represents errors through the built-in error interface. Error is an interface with an Error() string method. As long as the type implements the Error() string method, it can be returned as an error value. For example, use the fmt.Errorf() function to return a new error value:

func divide(x, y int) (int, error) {
  if y == 0 {
    return 0, fmt.Errorf("division by zero")
  }
  return x / y, nil
}

The above function divide returns two parameters, the first is the result of x/y, and the second is the error value, If y is zero, a new error value is returned. We can call this function as follows:

res, err := divide(6, 2)
if err != nil {
  fmt.Println(err)
  return
}
fmt.Println("Result is", res)

Note that when we call the function, we also check whether the second return value is nil. If it is not nil, it means that an error has occurred.

If we need to customize the error type, we can create a type to implement the error interface:

type myError struct {
  code    int
  message string
}
func (e *myError) Error() string {
  return fmt.Sprintf("Error code %d: %s", e.code, e.message)
}

Then, we can use this new error type in the following way:

func newMyError() error {
  return &myError{100, "custom error message"}
}

2. Best practices for error handling

1. Check all errors

In Go, it is a good programming habit to check all functions returning errors, which can help us find and fix potential bugs to ensure our programs don't break when errors occur.

2. Errors should contain readable information

When we return an error, we should add readable information, which can help users better understand the cause of the error.

3. Avoid using global error variables

Global error variables are not advisable because they may be misused by other unrelated code. Instead, we should return local variables in functions or methods, which avoids exposing errors to other functions.

4. Use the defer statement

Even if we return an error value in the function, we may still need to perform some cleanup operations, such as closing the file or releasing resources. To ensure that these cleanup operations are always performed, we can use the defer statement.

func myFunc() error {
  f, err := os.Open("file.txt")
  if err != nil {
    return err
  }
  defer f.Close()
  //其他代码
  return nil
}

Even after an error occurs in the function and returns, the defer statement will be executed before the function returns.

5. Error handling should not hinder the execution of the program

When handling errors, we should ensure that the error does not have a negative impact on the execution of the program. For example, if we have an error when decoding JSON Error, we can use the default value instead.

3. Summary

The error handling mechanism of Go language is a simple but powerful tool. It makes error handling very easy, which is a boon for Go language developers. . When writing Go programs, we should flexibly use the error handling mechanism and write good error handling code to avoid crashes or exceptions after program errors occur.

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