How Do Go Developers Compare Error Messages Without a `GetMessage()` Method?

Comparing Error Messages in Go

When handling errors in Java, developers often rely on the Exception.GetMessage() method to extract error descriptions. Golang, however, has no built-in method to retrieve such messages.

To address this, Go developers employ a custom approach to comparing error messages. Instead of storing messages within the error object, they create package-level error variables that encapsulate specific error codes or descriptions:

var errExample = errors.New("this is an example")

When returning errors, developers assign these variables to indicate the specific type of error that occurred. The following snippet demonstrates this approach:

if some_err := some_package.DoSomething(); some_err != nil {
    if some_err == errExample {
        // handle it
    }
}

In this case, the if statement checks if the error returned by DoSomething() is identical to the errExample variable. If so, the error is handled accordingly.

To extend the reach of these error variables, developers can export them outside the package using the export keyword:

var ErrExample = errors.New("this is an example")

This allows code in different packages to compare against the exported error variable:

if err == somepackage.ErrExample {
    // handle it
}

By following this approach, developers can effectively compare error messages in Golang, even though the language lacks a dedicated GetMessage() method.

Additional Considerations:

It's crucial to avoid comparing error messages against the string returned by the error.Error() method. This can make code brittle, as error messages are subject to change over time. Instead, it is recommended to use the established error variables to ensure consistency in error handling.

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