Do blocks guarantee local variables will be modified in Swift?

Question

func foo() -> Bool {
    var apiResult : Bool = false
    myAPI.bar() { (result: Bool) -> Void in
        // some logic in block and local variable assignment
        apiResult = result
    }
    return apiResult
}

Is the value of apiResult guaranteed to be updated by the block passed in? (I am a college student learning iOS, so please be as informative as possible)

Answer 1

You are passing the closure (block) to the myAPI.bar function. The function may or may not call the closure. If the closure is called then apiResult would change. The change may occur after the function foo returns though, depending on how myAPI.bar is implemented.