CODEWITHSUNDEEP
swiftfirebasememorygoogle-cloud-firestore
Omr
Omr

Reputation: 99

Save Memory when Loading Collection View

How would I go about saving memory when loading items into a collection view from a database? Suppose I have over 10,000 items in a database that is being retrieved (including images) into a collection view with multiple labels also being retrieved from the database.

Would I have to retrieve only the first 20-50 items and then create a function to retrieve the next set when the user has passed through the data or would it have more to do with the images?

Upvotes: 0

Views: 333

Answers (2)

sawarren
sawarren

Reputation: 306

Since iOS 10, you can prefetch data via the UICollectionViewDataSourcePrefetching protocol.

I would encourage you to download the sample and have a play around but essentially it allows you to:

  • fetch data before it's needed on screen.
  • load data asynchronously.
  • cancel unnecessary fetches.

In terms of memory concerns, both table views and collection views employ object pooling to reuse cell views, populating them with new data.

More specifically this is achieved by calling dequeueReusableCell(withReuseIdentifier:for:) within your implementation of the UICollectionViewDataSource method collectionView(_:cellForItemAt:)

An example of that is something along the lines of:

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    // Dequeues an existing cell if one is available, 
    // or creates a new one based on the registered class/nib.
    guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: Cell.reuseIdentifier, for: indexPath) as? Cell else {
        fatalError("Expected `\(Cell.self)` type for reuseIdentifier \(Cell.reuseIdentifier). Check the configuration in Main.storyboard.")
    }
    // Configure the cell for display.
    return cell
}

Happy coding :D

Upvotes: 1

ukim
ukim

Reputation: 2465

You should retrieve the data only when need. Core Data already has this ready for you. Take a look at NSFetchedResultsController.

Upvotes: 1

Related Questions