Move function void to boolean Swift - ios

Question

I am rookie with Swift. I need to change the following method to a boolean function which will return true if connection is ok else false if something is wrong. Thanks
func test() {
var configuration = SessionConfiguration()
configuration.host = "ftp://ftp.mozilla.org:21"
configuration.username = "optimus"
configuration.password = "rollout"
configuration.encoding = NSUTF8StringEncoding
_session = Session(configuration: configuration)
_session.list("/") {
(resources, error) -> Void in
println("List directory with result:\n\(resources), error: \(error)\n\n")
}
}

Answer 1

Since the _session.list("/") have a callback, which is asynchronous, what you can do is this:
func test(_ completion: (Bool) -> Void) {
// ...
_session.list("/") { (resources, error) -> Void in
println("List directory with result:\n\(resources), error: \(error)\n\n")
guard error == nil else {
completion(false) // failed
return
}
completion(true) // succeed
}
}
And so you can call it this way:
test() { (hasSucceeded: Bool) -> Void in
if hasSucceeded {
// Do what you want
} else {
// Failed
}
}

Answer 2

Lots of people have told you what to do, but nobody's clearly explained why.
The function _session.list() is an async function. When you call it it returns immediately, before it has even begun executing. The code runs on a separate thread, and the closure you pass in gets called once the function is complete.
Thus, you can't have your function return a simple bool. Async programming doesn't work that way.
Instead, you need to refactor your test function to take a closure with a bool parameter, as outlined by several other answers. (#KevinHirsch's answer for example.) Then when you invoke your test function you put the code that checks to see if the test passed or failed into the closure that you pass to the test function.

Answer 3

Since, session.list is an async process, add a completion handler and call your function as shown:
typealias theBool = (Bool) -> ()
func test(completion: theBool) {
//your code
_session.list("/") { (resources, error) in
guard error == nil else {
completion(false)
return
}
//your code
completion(true)
}
}
And call it like so:
test { someVar in
if someVar {
//do stuff when it is true
}
else{
//do stuff if it is false
}
}

Answer 4

When sync code:
func test() -> Bool {
return true
}
// Use case below:
let succes = test()
Turn to async use closure:
func test(didTest didTest: (Bool)->Void) {
...
_session.list("/") { (resources, error) -> Void in
if error != nil {
didTest(false)
} else {
didTest(true)
}
}
}
// Use case below:
test(didTest: { result in
let succes = result
})
Wish this may help.

Answer 5

Simply do
func test() -> Bool {
...
_session.list("/") { (resources, error) -> Void in
println("List directory with result:\n\(resources), error: \(error)\n\n")
if error != nil {
return true
} else {
return false
}
}
}
Updated:
I guess you should use closure for this because session.list is an async process. as #Duncan C said in his answer _session.list() When you call it it returns immediately, before it has even begun executing. The code runs on a separate thread, and the closure you pass in gets called once the function is complete.
public typealias SuccessClosure = (data: String) -> (Void)
public typealias FailureClosure = (error: NSError?, data: NSData? = nil, statusCode: Int? = nil) -> (Void)
func test(success: SuccessClosure, failure: FailureClosure) {
...
_session.list("/") { (resources, error) -> Void in
println("List directory with result:\n\(resources), error: \(error)\n\n")
if error != nil {
success("success")
} else {
failure(error)
}
}
}