How to create custom error type using Golang?

Creating a custom error type in Go requires the following steps: Create a new type using the error type as a base and add custom fields. Implement the Error() method in the error interface to return custom error information. Use custom error types in your code to return more descriptive error messages. These steps allow you to define custom error types, providing clearer error messages and simplifying debugging.

#How to create a custom error type in Go?

In Go, an error type is a special built-in type used to represent errors that occur during operations. By default, Go provides a built-in error type, but it is not a structured and valid data type and cannot convey more relevant contextual information. To solve this problem, Go allows you to define custom error types.

Create a custom error type

To create a custom error type, use the error type as a base and add additional fields to capture specific Error conditions:

type MyError struct {
    Code    int
    Message string
}

// implement the error interface
func (e *MyError) Error() string {
    return fmt.Sprintf("Code: %d, Message: %s", e.Code, e.Message)
}

By implementing the built-in error interface, the MyError type can be treated as the error type.

Using Custom Error Types

After creating custom error types, you can use them in your code to return more descriptive error information:

func MyFunction() error {
    if valid {
        return nil
    }
    return &MyError{
        Code:    400,
        Message: "Validation failed",
    }
}

Practical Case

Suppose you have a function that parses JSON into a structure, and you want to return a custom error code and message when the parsing fails. mistake. You can use a custom error type like this:

type JSONParseError struct {
    Code    int
    Message string
}

func (e *JSONParseError) Error() string {
    return fmt.Sprintf("Code: %d, Message: %s", e.Code, e.Message)
}

Then, your parsing function can use this error type to return a more specific error message:

func ParseJSON(data []byte) (result MyStruct, err error) {
    err = json.Unmarshal(data, &result)
    if err != nil {
        return result, &JSONParseError{
            Code:    500,
            Message: "Unable to parse JSON",
        }
    }
    return result, nil
}

By using a custom error type, you More informative and structured error handling can be provided, making debugging and problem resolution easier.

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