快速传递错误参数

Question

I am using a third party framework, in which it contains a class :

class DaService : NSObject {
    init!(name username: String!, error: AutoreleasingUnsafeMutablePointer<NSString?>)
    …
}

In my swift code, I create an instance of DaService :

let service = DaService(name: “My Name”, &err)

Compiler complains:

Use of unresolved identifier 'err'

Why this error? How to pass an error parameter in swift ?

Answer 1

I cannot test it currently, but it should be

var err : NSString? = nil
let service = DaService(name: "My Name", &err)

More information can be found in the "Autoreleasing Pointers" section in Interacting with C APIs .

Answer 2

you haven't initialized err before passing it. Working example:

class DaService : NSObject {
    init!(name username: String!, error: AutoreleasingUnsafeMutablePointer<NSString?>) {}

}

var err: NSString? = nil

let service = DaService(name: "My Name", error: &err)

Of course, better use swift2's throws and do/catch for error handling.

Answer 3

@MartinR is correct. AutoreleasingUnsafeMutablePointer<NSString?> means that the function intends to provide a NSString to you. You must give it a variable in which to put the string.

var errorString: NSString?
let service = DaService(name: "My Name", error: &errorString)