I was working with swift and got a question from somewhere but didn't understand what output will I get while running the function.
import UIKit
var i = 0
var closureArray : [() -> ()] = []
for _ in 1...5{
closureArray.append {
print(i)
}
i += 1
}
what will I get when I will type:-
closureArray[0]()
I know the answer but i want to know the explanation behind it.
You are appending functions body to closureArray with no return type as the function type has no input parameters and no return type.
So only closureArray will contains 5 blocks of functions.
Each element is itself a function with only one print operation which will print the array index. But if these are called after the for loop these always print the latest value of i
So closureArray[0]() will call the 0th indexed function that will print only "5" as the latest value of i is 5 and will return void.
Explanation is very simple.
This will always print 5 because you have defined a global variable, after traversing through the loop i=5. and after the loop, you are calling closure. which will always print 5. no matter the index of closureArray.
The value of i is only evaluated after calling closure.
Read Auto closure chapter swift4 guide:
https://docs.swift.org/swift-book/LanguageGuide/Closures.html
if you put closure calling inside for loop then it will print normally 'i' value i.e 0,1,2,3,4
for _ in 1...5{
closureArray.append {
print(i)
}
closureArray[0]()
i += 1
}
The functions appended in the closureArray is print(i) every time and the value of i is incremented for each iteration. The functions appended return void. So when you see the value of closureArray[0]() after each iteration it would print each value of i (i.e. 1 to 5) and return void. If you see the value of closureArray[0]() after the loop has executed it would return 5 and void. Moreover, for an array index, it would return the same value.
