Array in swift can grow dynamically according to the size, but it does not seem to be shrinking.
var x: [Int] = []
for i in 0...1000 {
x.append(i)
}
for i in reverse(1000...0) {
x.removeAtIndex(0)
}
The capacity of x remains large. I also tried removeLast() and copy it to a new variable, but does not seem to reduce the capacity.
To reset the capacity, use .removeAll(keepCapacity: false):
var x: [Int] = []
for i in 0...1000 {
x.append(i)
}
x.capacity // -> 1,532
x.removeAll(keepCapacity: false)
x.capacity // -> 0
If you want to keep the elements after optimizing the capacity, copy it with Array() constructor:
for i in 0...1000 {
x.append(i)
}
for i in reverse(0...999) {
x.removeAtIndex(0)
}
x.capacity // -> 1532
x = Array(x) // -> [1000]
x.capacity // -> 2
The growing/shrinking of the memory allocated by an array is part of the memory management of the runtime. Memory allocation might benefit from not directly de-allocating memory when the number of elements stored in the array is reduced. E.g., it may happen, that after elements were removed, new elements are added to the array. In that case, new memory would need to be allocated.
Also distinct between count and capacity.
