SwiftUI Realm Memory issue. RAM usage keeps on increasing - swiftui

Question

I am downloading over 7000 images that need to be saved to a Realm DB. I am writing to the DB in batches of 100. They are temporarily stored in an Array.
My issue is that as the process goes on, RAM usage keeps on increasing. I already wrapped the activity with autoreleasepool { activity }, but it keeps on happening.
func downloadImages() {
autoreleasepool {
realmQueue.async {
let realm = try! Realm()
print("6.5: Downloading Images")
var x = 0
var imageSavedArray : [ImageSaved] = []
let imageUrls = self.urlPrep()
for url1 in imageUrls {
let imageURL = URL(string: url1)
let placeholder = URL(string: "")
let imageToSave = ImageSaved()
if imageURL != nil {
let data = try? Data(contentsOf: imageURL)
imageToSave.link = url1
imageToSave.data = data
imageSavedArray.append(imageToSave)
} else {
print("Invalid Saving Process for " + url1)
}
if ((x % 100) == 0) {
try! realm.write {
realm.add(imageSavedArray)
}
imageSavedArray = []
}
x += 1
}//end for
}//end queue
} //end autoreleasepool
} //end function
[This will continue until eventually it crashes.][1]
As soon as the process finalizes, the RAM goes back to normal.As you can see, I am resetting the array after writing it to Realm.
Any help with this will be greatly appreciated.

Answer 1

Let me provide an answer using generic code to keep it brief, and ignore the .async for this answer.
Also, this code assumes the number of urls in the array is a multiple of 10 to keep it short.
for i in stride(from: 0, to: urlArray.count, by: 10) {
autoreleasepool(invoking: {
let smallUrlArray = myArray[i...i+9] //get 10 urls, start to fill pool
var imageSavedArray = [ImageSaved]()
for imageUrl in smallUrlArray {
let imageToSave = ...create an ImageSaved object from the image and data
imageSavedArray.append(imageToSave)
}
try! realm.write {
realm.add(imageSavedArray)
}
}) //drain pool
}
In the code, iterate over the array of urls every 10 indexes using stride
Within that outside loop, create an autorelease pool
Within the pool an array of 10 urls is created and then iterated over - within that loop, create the realm objects to save, store in an imageSavedArray, then write them to realm.
At the end of the closure, the pool is drained, meaning anything created inside the autorelease pool is disposed of and memory is freed.
So the memory profile looks like this
/| /|
/ | / |
/ | / |
fill^ ^drain