如何在集合视图中添加 indexTitles？ (iOS 10+)

Question

As the question, I'm trying to add an "index titles" in a collection view for a fast navigation of the contents of my UIColletionView .

I've read that, starting from iOS 10, method like indexTitles(for:) and collectionView(_:indexPathForIndexTitle:at:) can help me in that as in the UITableViews . But I'm not getting any result! Have you figured out how to use those methods? Thanks in advance for any help.

Answer 1

If you look at UICollectionView.h , indexTitlesForCollectionView is only available in tvos:

/// Returns a list of index titles to display in the index view (e.g. ["A", "B", "C" ... "Z", "#"])
- (nullable NSArray<NSString *> *)indexTitlesForCollectionView:(UICollectionView *)collectionView API_AVAILABLE(tvos(10.2));

You might have read Apple's documentation, which states that indexTitle methods are available for iOS 10.3+ and tvOS 10.2+: https://developer.apple.com/documentation/uikit/uicollectionviewdatasource/2851455-indextitles

I tried implementing it on iOS and it just doesn't work, which leads me to believe that somehow they made a mistake in the documentation.

Answer 2

I got the titles working on iPhones only by adding the following to my data source:

func indexTitles(for collectionView: UICollectionView) -> [String]? {
    guard !RunUtilities.isIpad else { return nil }
    return Array(Set(objects.map{ String($0.name.prefix(1)) })).sorted(by: { $0 < $1 })
}

func collectionView(_ collectionView: UICollectionView, indexPathForIndexTitle title: String, at index: Int) -> IndexPath {
    guard let index = objects.firstIndex(where: { $0.name.prefix(1) == title }) else {
        return IndexPath(item: 0, section: 0)
    }
    return IndexPath(item: index, section: 0)
}

EDIT: It looks like this is working from iOS 14 onwards. I installed the 13.4 runtime and the titles don't show.