Swift 2.0 - is the programming logic different from languages? - swift2

Question

I am new to Swift 2.0 programming. I made an app integrate with Parse. Following is the snippet of my code
private func isIdNotFound() ->Bool{
var notFound = true
let query = PFQuery(className: "Customer")
query.whereKey("customerId", equalTo: self.id)
query.findObjectsInBackgroundWithBlock{
(objects : [PFObject]?, error: NSError?) -> Void in
if error == nil && objects != nil{
print(objects)
notFound = false
print(notFound)
}
}
print(notFound)
return notFound
}
The console:
true
<Customer: 0x7feccbf07ef0, objectId: AiPH5pNgum, localId: (null)> {
customerId = wilson93;
email = 123;
password = 123;
}])
false
Why is it that it prints true then only it runs the logic and print false. As far as other languages such Java, it should print false twice.

Answer 1

As mentioned in comments, your code is query.findObjectsInBackgroundWithBlock:. Here, Background is the keyword. Because you are searching asynchronously, therefore not necessarily in the order the code is written, the second instance of print(notFound) is executed before the instance in the block.
You can tell because, if read out loud, the two print statements are right next to each other (excluding braces) but notFound is not printed twice in succession. objects is printed after the first (second instance in code) print statement but before the other one.
var notFound = true
query.findObjectsInBackgroundWithBlock{
(objects : [PFObject]?, error: NSError?) -> Void in
if error == nil && objects != nil{
print(objects) //this comes second
notFound = false
print(notFound) //then this comes last
}
}
print(notFound) //this runs first
See the documentation for PFQuery here. It says, in italics, that the search is performed asynchronously.
From the doc:
Finds objects asynchronously and calls the given block with the results.
- (void)findObjectsInBackgroundWithBlock:(nullable PFQueryArrayResultBlock)block
Parameters
IIRC, this means that the search is run on another thread.
#Community correct me if I'm wrong.