So in practice, this means that %s and %v are identical, except when a golang curl Format() method exists on the error type (or when the error is nil). In the other 0.001% of cases, %v and %s probably “should” behave the same, except when the error value is nil, but there are no guarantees. The friendlier output of %v for nil errors may be reason to prefer %v (see below). %s %v and %w can be used to format errors in Go (turn them into strings with fmt.Errorf). But, In Go 1.13, the fmt.Errorf function supports a new %w verb.
Use %w instead of %v or %s:
- Please note the links to the Go specification which speak at greater length to the operators.
- The friendlier output of %v for nil errors may be reason to prefer %v (see below).
- You are thinking it’s related to assignment as in other languages.
- In all other ways, %w is identical to %v.
- You cannot use the operators interchangeably because of a type mismatch.
The details for how %s and %v are implemented are available in the docs. I’ve highlighted the parts relevant to your question. You are thinking it’s related to assignment as in other languages. In your code, a value “j” is being sent to the channel “jobs”. You cannot use the operators interchangeably because of a type mismatch.
Okay, so what about %v and %s?
- In your code, a value “j” is being sent to the channel “jobs”.
- And finally, if your error type supports the %+v verb variant, then you will, of course, need to use that, if you desire the detailed output.
- I’ve highlighted the parts relevant to your question.
- In the other 0.001% of cases, %v and %s probably “should” behave the same, except when the error value is nil, but there are no guarantees.
When this verb is present, the error returned by fmt.Errorf will have an Unwrap method returning the argument of %w, which must be an error. In all other ways, %w is identical to %v. And finally, if your error type supports the %+v verb variant, then you will, of course, need to use that, if you desire the detailed output.
Your Answer
Please note the links to the Go specification which speak at greater length to the operators.
