Using String's enumerateLines function in Swift - swift

Question

The enumerateLines function of Swift's String type is declared like this:
enumerateLines(body: (line: String, inout stop: Bool) -> ())
As I understand it, this declaration means: "enumerateLines is a function taking a closure, body, which is handed two variables, line and stop, and returns void."
According to the Swift Programming Language book, I believe I should thus be able to call enumerateLines in a nice terse fashion with a trailing closure, like this:
var someString = "Hello"
someString.enumerateLines()
{
// Do something with the line here
}
..but that results in a compiler error:
Tuple types '(line: String, inout stop: Bool)' and '()' have a different number of elements (2 vs. 0)
So then I try explicitly putting in the arguments, and doing away with the trailing closure:
addressString.enumerateLines((line: String, stop: Bool)
{
// Do something with the line here
})
...but that results in the error:
'(() -> () -> $T2) -> $T3' is not identical to '(line: String.Type, stop: Bool.Type)'
In short, no syntax that I've tried has resulted in anything that will successfully compile.
Could anybody point out the error in my understanding and provide a syntax that will work please? I'm using Xcode 6 Beta 4.

Answer 1

The closure expression syntax has the general form
{ (parameters) -> return type in
statements
}
In this case:
addressString.enumerateLines ({
(line: String, inout stop: Bool) -> () in
println(line)
})
Or, using the trailing closure syntax:
addressString.enumerateLines {
(line: String, inout stop: Bool) in
println(line)
}
Due to automatic type inference, this can be shortened to
addressString.enumerateLines {
line, stop in
println(line)
}
Update for Swift 3:
addressString.enumerateLines { (line, stop) in
print(line)
// Optionally:
if someCondition { stop = true }
}
Or, if you don't need the "stop" parameter:
addressString.enumerateLines { (line, _) in
print(line)
}