So in practice, this means that %s and %v are identical, except when a 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.
Answers 4
- Please note the links to the Go specification which speak at greater length to the operators.
- The details for how %s and %v are implemented are available in the docs.
- You cannot use the operators interchangeably because of a type mismatch.
- In all other ways, %w is identical to %v.
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.
Format errors in Go – %s %v or %w
When this verb is present, the error returned by golang curl 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
- The friendlier output of %v for nil errors may be reason to prefer %v (see below).
- I’ve highlighted the parts relevant to your question.
- 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.
- You are thinking it’s related to assignment as in other languages.
- But, In Go 1.13, the fmt.Errorf function supports a new %w verb.
Please note the links to the Go specification which speak at greater length to the operators.