How Can I Gracefully Handle Custom Error Types in Go?

Handling Custom Error Types in Go

You encounter difficulties utilizing custom error types in Go. After referring to a blog post on errors, you attempt to define a custom error type ModelMissingError but face an error when checking its type.

To resolve this issue, you need to use the "comma ok" idiom:

serr, ok := err.(*model.ModelMissingError)

This idiom allows you to assert the type of an interface value and obtain the underlying concrete value. In this case, the error variable err is tested to see if it holds a concrete type of *model.ModelMissingError.

If the assertion is successful, ok will be set to true and serr will hold the underlying *model.ModelMissingError value. You can then use this value to take appropriate actions based on the custom error.

For example, you can modify your code to:

if ok && serr.msg == "no model found for id" {
    // Handle error gracefully
}

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