Iterate For Loop Overtime in Swift

How can I iterate a for loop overtime in swift? A typical loop will execute immediately as fast as possible. However, I would like to expand the time in which the loop occurs. Say I have the following loop:

for var i = 0; i < 4; i+=1{
        print(i)
}

And I wanted this loop to occur over a span of 1 second, each iteration taking 0.25 seconds. How could I do this? Thanks for any help