Returns a new result, mapping any failure value using the given transformation.
- Xcode 10.2+
- Swift Standard Library
A closure that takes the failure value of the instance.
Result instance with the result of evaluating
transform as the new failure value if this instance represents a failure.
Use this method when you need to transform the value of a
Result instance when it represents a failure. The following example transforms the error value of a result by wrapping it in a custom