How to pass an error pointer in the Swift language?

Question

I am attempting to pass an error pointer in swift and am unable to do so. The compiler complains that "NSError is not convertible to 'NSErrorPointer'".

var error: NSError = NSError() var results = context.executeFetchRequest(request, error: error)  if(error != nil) {     println("Error executing request for entity \(entity)") } 

Answer 1

You just pass a reference like so:

var error: NSError? var results = context.executeFetchRequest(request, error: &error)  if error != nil {     println("Error executing request for entity \(entity)") } 

Two important points here:

1. NSError? is an optional (and initialized to nil)
2. you pass by reference using the & operator (e.g., &error)

See: Using swift with cocoa and objective-c

Answer 2

This suggestion is up for discussion, but some engineers would prefer to use the golden path syntax:

var maybeError: NSError? if let results = context.executeFetchRequest(request, error: &maybeError) {     // Work with results } else if let error = maybeError {     // Handle the error }