How do you make a long list fast: List, LazyVStack and stable ids?
The gist
A long list's speed comes down to three things: how many rows are actually created, how expensive each row's body is, and how stable the identifiers are. A VStack inside a ScrollView creates all rows at once — with hundreds of items that is already noticeable. LazyVStack and List create rows as they approach the visible area. On iOS 16+ List is built on top of UICollectionView and reuses cells; LazyVStack creates rows lazily but does not reuse cells that way, so for very long feeds with complex rows List is usually more memory-efficient.
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